diff --git a/baselines/dom.generated.d.ts b/baselines/dom.generated.d.ts
index b9bd67fc5..7b4ddefbb 100644
--- a/baselines/dom.generated.d.ts
+++ b/baselines/dom.generated.d.ts
@@ -35284,7 +35284,7 @@ interface Scheduler {
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Scheduler/postTask)
      */
-    postTask(callback: SchedulerPostTaskCallback, options?: SchedulerPostTaskOptions): Promise<any>;
+    postTask<T = any>(callback: SchedulerPostTaskCallback<T>, options?: SchedulerPostTaskOptions): Promise<T>;
     /**
      * The **`yield()`** method of the Scheduler interface is used for yielding to the main thread during a task and continuing execution later, with the continuation scheduled as a prioritized task (see the Prioritized Task Scheduling API for more information). This allows long-running work to be broken up so the browser stays responsive.
      *
@@ -43919,8 +43919,8 @@ interface ResizeObserverCallback {
     (entries: ResizeObserverEntry[], observer: ResizeObserver): void;
 }
 
-interface SchedulerPostTaskCallback {
-    (): any;
+interface SchedulerPostTaskCallback<T = any> {
+    (): T | PromiseLike<T>;
 }
 
 interface TransformerFlushCallback<O> {
diff --git a/baselines/serviceworker.generated.d.ts b/baselines/serviceworker.generated.d.ts
index 56359a693..bf2af6371 100644
--- a/baselines/serviceworker.generated.d.ts
+++ b/baselines/serviceworker.generated.d.ts
@@ -8558,7 +8558,7 @@ interface Scheduler {
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Scheduler/postTask)
      */
-    postTask(callback: SchedulerPostTaskCallback, options?: SchedulerPostTaskOptions): Promise<any>;
+    postTask<T = any>(callback: SchedulerPostTaskCallback<T>, options?: SchedulerPostTaskOptions): Promise<T>;
     /**
      * The **`yield()`** method of the Scheduler interface is used for yielding to the main thread during a task and continuing execution later, with the continuation scheduled as a prioritized task (see the Prioritized Task Scheduling API for more information). This allows long-running work to be broken up so the browser stays responsive.
      *
@@ -13349,8 +13349,8 @@ interface ReportingObserverCallback {
     (reports: Report[], observer: ReportingObserver): void;
 }
 
-interface SchedulerPostTaskCallback {
-    (): any;
+interface SchedulerPostTaskCallback<T = any> {
+    (): T | PromiseLike<T>;
 }
 
 interface TransformerFlushCallback<O> {
diff --git a/baselines/sharedworker.generated.d.ts b/baselines/sharedworker.generated.d.ts
index 6db80ae55..0aa57c3f9 100644
--- a/baselines/sharedworker.generated.d.ts
+++ b/baselines/sharedworker.generated.d.ts
@@ -8141,7 +8141,7 @@ interface Scheduler {
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Scheduler/postTask)
      */
-    postTask(callback: SchedulerPostTaskCallback, options?: SchedulerPostTaskOptions): Promise<any>;
+    postTask<T = any>(callback: SchedulerPostTaskCallback<T>, options?: SchedulerPostTaskOptions): Promise<T>;
     /**
      * The **`yield()`** method of the Scheduler interface is used for yielding to the main thread during a task and continuing execution later, with the continuation scheduled as a prioritized task (see the Prioritized Task Scheduling API for more information). This allows long-running work to be broken up so the browser stays responsive.
      *
@@ -13075,8 +13075,8 @@ interface ReportingObserverCallback {
     (reports: Report[], observer: ReportingObserver): void;
 }
 
-interface SchedulerPostTaskCallback {
-    (): any;
+interface SchedulerPostTaskCallback<T = any> {
+    (): T | PromiseLike<T>;
 }
 
 interface TransformerFlushCallback<O> {
diff --git a/baselines/ts5.5/dom.generated.d.ts b/baselines/ts5.5/dom.generated.d.ts
index e34301255..408304b71 100644
--- a/baselines/ts5.5/dom.generated.d.ts
+++ b/baselines/ts5.5/dom.generated.d.ts
@@ -35259,7 +35259,7 @@ interface Scheduler {
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Scheduler/postTask)
      */
-    postTask(callback: SchedulerPostTaskCallback, options?: SchedulerPostTaskOptions): Promise<any>;
+    postTask<T = any>(callback: SchedulerPostTaskCallback<T>, options?: SchedulerPostTaskOptions): Promise<T>;
     /**
      * The **`yield()`** method of the Scheduler interface is used for yielding to the main thread during a task and continuing execution later, with the continuation scheduled as a prioritized task (see the Prioritized Task Scheduling API for more information). This allows long-running work to be broken up so the browser stays responsive.
      *
@@ -43893,8 +43893,8 @@ interface ResizeObserverCallback {
     (entries: ResizeObserverEntry[], observer: ResizeObserver): void;
 }
 
-interface SchedulerPostTaskCallback {
-    (): any;
+interface SchedulerPostTaskCallback<T = any> {
+    (): T | PromiseLike<T>;
 }
 
 interface TransformerFlushCallback<O> {
diff --git a/baselines/ts5.5/serviceworker.generated.d.ts b/baselines/ts5.5/serviceworker.generated.d.ts
index 19ecf148c..fe5c41d15 100644
--- a/baselines/ts5.5/serviceworker.generated.d.ts
+++ b/baselines/ts5.5/serviceworker.generated.d.ts
@@ -8555,7 +8555,7 @@ interface Scheduler {
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Scheduler/postTask)
      */
-    postTask(callback: SchedulerPostTaskCallback, options?: SchedulerPostTaskOptions): Promise<any>;
+    postTask<T = any>(callback: SchedulerPostTaskCallback<T>, options?: SchedulerPostTaskOptions): Promise<T>;
     /**
      * The **`yield()`** method of the Scheduler interface is used for yielding to the main thread during a task and continuing execution later, with the continuation scheduled as a prioritized task (see the Prioritized Task Scheduling API for more information). This allows long-running work to be broken up so the browser stays responsive.
      *
@@ -13346,8 +13346,8 @@ interface ReportingObserverCallback {
     (reports: Report[], observer: ReportingObserver): void;
 }
 
-interface SchedulerPostTaskCallback {
-    (): any;
+interface SchedulerPostTaskCallback<T = any> {
+    (): T | PromiseLike<T>;
 }
 
 interface TransformerFlushCallback<O> {
diff --git a/baselines/ts5.5/sharedworker.generated.d.ts b/baselines/ts5.5/sharedworker.generated.d.ts
index c417dc5a0..812fb3da4 100644
--- a/baselines/ts5.5/sharedworker.generated.d.ts
+++ b/baselines/ts5.5/sharedworker.generated.d.ts
@@ -8138,7 +8138,7 @@ interface Scheduler {
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Scheduler/postTask)
      */
-    postTask(callback: SchedulerPostTaskCallback, options?: SchedulerPostTaskOptions): Promise<any>;
+    postTask<T = any>(callback: SchedulerPostTaskCallback<T>, options?: SchedulerPostTaskOptions): Promise<T>;
     /**
      * The **`yield()`** method of the Scheduler interface is used for yielding to the main thread during a task and continuing execution later, with the continuation scheduled as a prioritized task (see the Prioritized Task Scheduling API for more information). This allows long-running work to be broken up so the browser stays responsive.
      *
@@ -13072,8 +13072,8 @@ interface ReportingObserverCallback {
     (reports: Report[], observer: ReportingObserver): void;
 }
 
-interface SchedulerPostTaskCallback {
-    (): any;
+interface SchedulerPostTaskCallback<T = any> {
+    (): T | PromiseLike<T>;
 }
 
 interface TransformerFlushCallback<O> {
diff --git a/baselines/ts5.5/webworker.generated.d.ts b/baselines/ts5.5/webworker.generated.d.ts
index 66053df45..4379bc659 100644
--- a/baselines/ts5.5/webworker.generated.d.ts
+++ b/baselines/ts5.5/webworker.generated.d.ts
@@ -9706,7 +9706,7 @@ interface Scheduler {
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Scheduler/postTask)
      */
-    postTask(callback: SchedulerPostTaskCallback, options?: SchedulerPostTaskOptions): Promise<any>;
+    postTask<T = any>(callback: SchedulerPostTaskCallback<T>, options?: SchedulerPostTaskOptions): Promise<T>;
     /**
      * The **`yield()`** method of the Scheduler interface is used for yielding to the main thread during a task and continuing execution later, with the continuation scheduled as a prioritized task (see the Prioritized Task Scheduling API for more information). This allows long-running work to be broken up so the browser stays responsive.
      *
@@ -15172,8 +15172,8 @@ interface ReportingObserverCallback {
     (reports: Report[], observer: ReportingObserver): void;
 }
 
-interface SchedulerPostTaskCallback {
-    (): any;
+interface SchedulerPostTaskCallback<T = any> {
+    (): T | PromiseLike<T>;
 }
 
 interface TransformerFlushCallback<O> {
diff --git a/baselines/ts5.6/dom.generated.d.ts b/baselines/ts5.6/dom.generated.d.ts
index a22d318bc..2b83c354c 100644
--- a/baselines/ts5.6/dom.generated.d.ts
+++ b/baselines/ts5.6/dom.generated.d.ts
@@ -35281,7 +35281,7 @@ interface Scheduler {
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Scheduler/postTask)
      */
-    postTask(callback: SchedulerPostTaskCallback, options?: SchedulerPostTaskOptions): Promise<any>;
+    postTask<T = any>(callback: SchedulerPostTaskCallback<T>, options?: SchedulerPostTaskOptions): Promise<T>;
     /**
      * The **`yield()`** method of the Scheduler interface is used for yielding to the main thread during a task and continuing execution later, with the continuation scheduled as a prioritized task (see the Prioritized Task Scheduling API for more information). This allows long-running work to be broken up so the browser stays responsive.
      *
@@ -43916,8 +43916,8 @@ interface ResizeObserverCallback {
     (entries: ResizeObserverEntry[], observer: ResizeObserver): void;
 }
 
-interface SchedulerPostTaskCallback {
-    (): any;
+interface SchedulerPostTaskCallback<T = any> {
+    (): T | PromiseLike<T>;
 }
 
 interface TransformerFlushCallback<O> {
diff --git a/baselines/ts5.6/serviceworker.generated.d.ts b/baselines/ts5.6/serviceworker.generated.d.ts
index 19ecf148c..fe5c41d15 100644
--- a/baselines/ts5.6/serviceworker.generated.d.ts
+++ b/baselines/ts5.6/serviceworker.generated.d.ts
@@ -8555,7 +8555,7 @@ interface Scheduler {
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Scheduler/postTask)
      */
-    postTask(callback: SchedulerPostTaskCallback, options?: SchedulerPostTaskOptions): Promise<any>;
+    postTask<T = any>(callback: SchedulerPostTaskCallback<T>, options?: SchedulerPostTaskOptions): Promise<T>;
     /**
      * The **`yield()`** method of the Scheduler interface is used for yielding to the main thread during a task and continuing execution later, with the continuation scheduled as a prioritized task (see the Prioritized Task Scheduling API for more information). This allows long-running work to be broken up so the browser stays responsive.
      *
@@ -13346,8 +13346,8 @@ interface ReportingObserverCallback {
     (reports: Report[], observer: ReportingObserver): void;
 }
 
-interface SchedulerPostTaskCallback {
-    (): any;
+interface SchedulerPostTaskCallback<T = any> {
+    (): T | PromiseLike<T>;
 }
 
 interface TransformerFlushCallback<O> {
diff --git a/baselines/ts5.6/sharedworker.generated.d.ts b/baselines/ts5.6/sharedworker.generated.d.ts
index c417dc5a0..812fb3da4 100644
--- a/baselines/ts5.6/sharedworker.generated.d.ts
+++ b/baselines/ts5.6/sharedworker.generated.d.ts
@@ -8138,7 +8138,7 @@ interface Scheduler {
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Scheduler/postTask)
      */
-    postTask(callback: SchedulerPostTaskCallback, options?: SchedulerPostTaskOptions): Promise<any>;
+    postTask<T = any>(callback: SchedulerPostTaskCallback<T>, options?: SchedulerPostTaskOptions): Promise<T>;
     /**
      * The **`yield()`** method of the Scheduler interface is used for yielding to the main thread during a task and continuing execution later, with the continuation scheduled as a prioritized task (see the Prioritized Task Scheduling API for more information). This allows long-running work to be broken up so the browser stays responsive.
      *
@@ -13072,8 +13072,8 @@ interface ReportingObserverCallback {
     (reports: Report[], observer: ReportingObserver): void;
 }
 
-interface SchedulerPostTaskCallback {
-    (): any;
+interface SchedulerPostTaskCallback<T = any> {
+    (): T | PromiseLike<T>;
 }
 
 interface TransformerFlushCallback<O> {
diff --git a/baselines/ts5.6/webworker.generated.d.ts b/baselines/ts5.6/webworker.generated.d.ts
index 66053df45..4379bc659 100644
--- a/baselines/ts5.6/webworker.generated.d.ts
+++ b/baselines/ts5.6/webworker.generated.d.ts
@@ -9706,7 +9706,7 @@ interface Scheduler {
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Scheduler/postTask)
      */
-    postTask(callback: SchedulerPostTaskCallback, options?: SchedulerPostTaskOptions): Promise<any>;
+    postTask<T = any>(callback: SchedulerPostTaskCallback<T>, options?: SchedulerPostTaskOptions): Promise<T>;
     /**
      * The **`yield()`** method of the Scheduler interface is used for yielding to the main thread during a task and continuing execution later, with the continuation scheduled as a prioritized task (see the Prioritized Task Scheduling API for more information). This allows long-running work to be broken up so the browser stays responsive.
      *
@@ -15172,8 +15172,8 @@ interface ReportingObserverCallback {
     (reports: Report[], observer: ReportingObserver): void;
 }
 
-interface SchedulerPostTaskCallback {
-    (): any;
+interface SchedulerPostTaskCallback<T = any> {
+    (): T | PromiseLike<T>;
 }
 
 interface TransformerFlushCallback<O> {
diff --git a/baselines/ts5.9/dom.generated.d.ts b/baselines/ts5.9/dom.generated.d.ts
index e63d5bfbb..8c3c61b95 100644
--- a/baselines/ts5.9/dom.generated.d.ts
+++ b/baselines/ts5.9/dom.generated.d.ts
@@ -35281,7 +35281,7 @@ interface Scheduler {
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Scheduler/postTask)
      */
-    postTask(callback: SchedulerPostTaskCallback, options?: SchedulerPostTaskOptions): Promise<any>;
+    postTask<T = any>(callback: SchedulerPostTaskCallback<T>, options?: SchedulerPostTaskOptions): Promise<T>;
     /**
      * The **`yield()`** method of the Scheduler interface is used for yielding to the main thread during a task and continuing execution later, with the continuation scheduled as a prioritized task (see the Prioritized Task Scheduling API for more information). This allows long-running work to be broken up so the browser stays responsive.
      *
@@ -43916,8 +43916,8 @@ interface ResizeObserverCallback {
     (entries: ResizeObserverEntry[], observer: ResizeObserver): void;
 }
 
-interface SchedulerPostTaskCallback {
-    (): any;
+interface SchedulerPostTaskCallback<T = any> {
+    (): T | PromiseLike<T>;
 }
 
 interface TransformerFlushCallback<O> {
diff --git a/baselines/ts5.9/serviceworker.generated.d.ts b/baselines/ts5.9/serviceworker.generated.d.ts
index b9940a22d..01e6d5359 100644
--- a/baselines/ts5.9/serviceworker.generated.d.ts
+++ b/baselines/ts5.9/serviceworker.generated.d.ts
@@ -8555,7 +8555,7 @@ interface Scheduler {
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Scheduler/postTask)
      */
-    postTask(callback: SchedulerPostTaskCallback, options?: SchedulerPostTaskOptions): Promise<any>;
+    postTask<T = any>(callback: SchedulerPostTaskCallback<T>, options?: SchedulerPostTaskOptions): Promise<T>;
     /**
      * The **`yield()`** method of the Scheduler interface is used for yielding to the main thread during a task and continuing execution later, with the continuation scheduled as a prioritized task (see the Prioritized Task Scheduling API for more information). This allows long-running work to be broken up so the browser stays responsive.
      *
@@ -13346,8 +13346,8 @@ interface ReportingObserverCallback {
     (reports: Report[], observer: ReportingObserver): void;
 }
 
-interface SchedulerPostTaskCallback {
-    (): any;
+interface SchedulerPostTaskCallback<T = any> {
+    (): T | PromiseLike<T>;
 }
 
 interface TransformerFlushCallback<O> {
diff --git a/baselines/ts5.9/sharedworker.generated.d.ts b/baselines/ts5.9/sharedworker.generated.d.ts
index 03574cee1..3feb5ab32 100644
--- a/baselines/ts5.9/sharedworker.generated.d.ts
+++ b/baselines/ts5.9/sharedworker.generated.d.ts
@@ -8138,7 +8138,7 @@ interface Scheduler {
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Scheduler/postTask)
      */
-    postTask(callback: SchedulerPostTaskCallback, options?: SchedulerPostTaskOptions): Promise<any>;
+    postTask<T = any>(callback: SchedulerPostTaskCallback<T>, options?: SchedulerPostTaskOptions): Promise<T>;
     /**
      * The **`yield()`** method of the Scheduler interface is used for yielding to the main thread during a task and continuing execution later, with the continuation scheduled as a prioritized task (see the Prioritized Task Scheduling API for more information). This allows long-running work to be broken up so the browser stays responsive.
      *
@@ -13072,8 +13072,8 @@ interface ReportingObserverCallback {
     (reports: Report[], observer: ReportingObserver): void;
 }
 
-interface SchedulerPostTaskCallback {
-    (): any;
+interface SchedulerPostTaskCallback<T = any> {
+    (): T | PromiseLike<T>;
 }
 
 interface TransformerFlushCallback<O> {
diff --git a/baselines/ts5.9/webworker.generated.d.ts b/baselines/ts5.9/webworker.generated.d.ts
index 8d4b90af9..ad8845d32 100644
--- a/baselines/ts5.9/webworker.generated.d.ts
+++ b/baselines/ts5.9/webworker.generated.d.ts
@@ -9706,7 +9706,7 @@ interface Scheduler {
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Scheduler/postTask)
      */
-    postTask(callback: SchedulerPostTaskCallback, options?: SchedulerPostTaskOptions): Promise<any>;
+    postTask<T = any>(callback: SchedulerPostTaskCallback<T>, options?: SchedulerPostTaskOptions): Promise<T>;
     /**
      * The **`yield()`** method of the Scheduler interface is used for yielding to the main thread during a task and continuing execution later, with the continuation scheduled as a prioritized task (see the Prioritized Task Scheduling API for more information). This allows long-running work to be broken up so the browser stays responsive.
      *
@@ -15172,8 +15172,8 @@ interface ReportingObserverCallback {
     (reports: Report[], observer: ReportingObserver): void;
 }
 
-interface SchedulerPostTaskCallback {
-    (): any;
+interface SchedulerPostTaskCallback<T = any> {
+    (): T | PromiseLike<T>;
 }
 
 interface TransformerFlushCallback<O> {
diff --git a/baselines/webworker.generated.d.ts b/baselines/webworker.generated.d.ts
index a9cdc506c..d83899699 100644
--- a/baselines/webworker.generated.d.ts
+++ b/baselines/webworker.generated.d.ts
@@ -9709,7 +9709,7 @@ interface Scheduler {
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Scheduler/postTask)
      */
-    postTask(callback: SchedulerPostTaskCallback, options?: SchedulerPostTaskOptions): Promise<any>;
+    postTask<T = any>(callback: SchedulerPostTaskCallback<T>, options?: SchedulerPostTaskOptions): Promise<T>;
     /**
      * The **`yield()`** method of the Scheduler interface is used for yielding to the main thread during a task and continuing execution later, with the continuation scheduled as a prioritized task (see the Prioritized Task Scheduling API for more information). This allows long-running work to be broken up so the browser stays responsive.
      *
@@ -15175,8 +15175,8 @@ interface ReportingObserverCallback {
     (reports: Report[], observer: ReportingObserver): void;
 }
 
-interface SchedulerPostTaskCallback {
-    (): any;
+interface SchedulerPostTaskCallback<T = any> {
+    (): T | PromiseLike<T>;
 }
 
 interface TransformerFlushCallback<O> {
diff --git a/inputfiles/overridingTypes.jsonc b/inputfiles/overridingTypes.jsonc
index b20f538ba..dd140e04c 100644
--- a/inputfiles/overridingTypes.jsonc
+++ b/inputfiles/overridingTypes.jsonc
@@ -124,6 +124,19 @@
                     }
                 }
             },
+            "SchedulerPostTaskCallback": {
+                "typeParameters": [
+                    {
+                        "name": "T",
+                        "default": "any"
+                    }
+                ],
+                "signature": {
+                    "0": {
+                        "overrideType": "T | PromiseLike<T>"
+                    }
+                }
+            },
             "UnderlyingSourceStartCallback": {
                 "typeParameters": [
                     {
@@ -1891,6 +1904,31 @@
                     ]
                 }
             },
+            "Scheduler": {
+                "methods": {
+                    "method": {
+                        "postTask": {
+                            "signature": {
+                                "0": {
+                                    "typeParameters": [
+                                        {
+                                            "name": "T",
+                                            "default": "any"
+                                        }
+                                    ],
+                                    "param": [
+                                        {
+                                            "name": "callback",
+                                            "overrideType": "SchedulerPostTaskCallback<T>"
+                                        }
+                                    ],
+                                    "overrideType": "Promise<T>"
+                                }
+                            }
+                        }
+                    }
+                }
+            },
             "MessagePort": {
                 "methods": {
                     "method": {
diff --git a/unittests/files/schedulerPostTask.ts b/unittests/files/schedulerPostTask.ts
new file mode 100644
index 000000000..da320e638
--- /dev/null
+++ b/unittests/files/schedulerPostTask.ts
@@ -0,0 +1,26 @@
+function assertType<T>(_x: T) {}
+
+type Equals<A, B> =
+  (<T>() => T extends A ? 1 : 2) extends <T>() => T extends B ? 1 : 2
+    ? true
+    : false;
+declare function assertExact<T extends true>(): void;
+
+async function testSchedulerPostTask() {
+  const num = await scheduler.postTask(() => 42);
+  assertExact<Equals<typeof num, number>>();
+
+  const str = await scheduler.postTask(async () => "done", {
+    priority: "background",
+  });
+  assertExact<Equals<typeof str, string>>();
+
+  const nothing = await scheduler.postTask(() => {});
+  assertExact<Equals<typeof nothing, void>>();
+
+  // @ts-expect-error The result is a number, not a string.
+  assertType<string>(await scheduler.postTask(() => 42));
+
+  // An explicit `any` type argument keeps the previous behavior.
+  assertType<Promise<any>>(scheduler.postTask<any>(() => 1));
+}