diff --git a/docs/ci/TestingOnCI.md b/docs/ci/TestingOnCI.md
index 1c97b29c0fe..f9da01e4c08 100644
--- a/docs/ci/TestingOnCI.md
+++ b/docs/ci/TestingOnCI.md
@@ -216,7 +216,7 @@ If no `Partition` traits are found, the infrastructure automatically falls back
 
 ## Controlling OS Compatibility
 
-By default, tests run on all three platforms. To restrict a project to specific OSes:
+By default, tests run on Linux and Windows. macOS is **disabled by default** — only tests that explicitly opt in will run on macOS. To configure which OSes a project runs on:
 
 ```xml
 <PropertyGroup>
@@ -227,6 +227,15 @@ By default, tests run on all three platforms. To restrict a project to specific
 </PropertyGroup>
 ```
 
+To opt a project into macOS runs (e.g., only on push/merge, not on pull requests):
+
+```xml
+<PropertyGroup>
+  <!-- Run on macOS in GitHub Actions, but only outside of pull requests -->
+  <RunOnGithubActionsMacOS Condition=" '$(IsGitHubActionsRunner)' == 'true' and '$(IsGithubPullRequest)' != 'true' ">true</RunOnGithubActionsMacOS>
+</PropertyGroup>
+```
+
 ## Requiring NuGet Packages
 
 For tests that need the built Aspire packages (e.g., template tests, end-to-end tests):
diff --git a/eng/Testing.targets b/eng/Testing.targets
index e55b7843447..48387ba5b85 100644
--- a/eng/Testing.targets
+++ b/eng/Testing.targets
@@ -12,7 +12,7 @@
       Project requirements:
         - RunOnGithubActions:          indicates whether tests should run on GitHub Actions (either Windows or Linux or macOS); computed.
         - RunOnGithubActionsWindows:   indicates whether tests should run on Windows in GitHub Actions; default is true; overridable.
-        - RunOnGithubActionsMacOS:     indicates whether tests should run on MacOS in GitHub Actions; default is false on pull requests and true otherwise; overridable.
+        - RunOnGithubActionsMacOS:     indicates whether tests should run on MacOS in GitHub Actions; default is false; overridable.
         - RunOnGithubActionsLinux:     indicates whether tests should run on Linux in GitHub Actions; default is true; overridable.
         - RunOnAzdoCI:                 indicates whether tests should run on Azure DevOps (either Windows or Linux); always false, if RunOnAzdoHelix=true; computed.
         - RunOnAzdoCIWindows:          indicates whether tests should run on Windows in Azure DevOps; default is true; overridable.
@@ -49,8 +49,9 @@
   </PropertyGroup>
 
   <PropertyGroup>
-    <RunOnGithubActionsMacOS Condition=" '$(RunOnGithubActionsMacOS)' == '' and '$(IsGithubPullRequest)' == 'true' ">false</RunOnGithubActionsMacOS>
-    <RunOnGithubActionsMacOS Condition=" '$(RunOnGithubActionsMacOS)' == '' ">true</RunOnGithubActionsMacOS>
+    <!-- See https://github.com/microsoft/aspire/issues/15615 -->
+    <!-- <RunOnGithubActionsMacOS Condition=" '$(RunOnGithubActionsMacOS)' == '' and '$(IsGithubPullRequest)' == 'true' ">false</RunOnGithubActionsMacOS> -->
+    <RunOnGithubActionsMacOS Condition=" '$(RunOnGithubActionsMacOS)' == '' ">false</RunOnGithubActionsMacOS>
 
     <RunOnGithubActions>false</RunOnGithubActions>
     <RunOnGithubActions Condition=" '$(RunOnGithubActionsWindows)' == 'true' or '$(RunOnGithubActionsLinux)' == 'true' or '$(RunOnGithubActionsMacOS)' == 'true' ">true</RunOnGithubActions>
diff --git a/tests/Aspire.Templates.Tests/Aspire.Templates.Tests.csproj b/tests/Aspire.Templates.Tests/Aspire.Templates.Tests.csproj
index e9a74f4a277..567c2635495 100644
--- a/tests/Aspire.Templates.Tests/Aspire.Templates.Tests.csproj
+++ b/tests/Aspire.Templates.Tests/Aspire.Templates.Tests.csproj
@@ -25,6 +25,9 @@
     <RunOnAzdoCIWindows>false</RunOnAzdoCIWindows>
     <RunOnAzdoCILinux>false</RunOnAzdoCILinux>
 
+    <!-- run on macOS in GitHub Actions, but only outside of pull requests -->
+    <RunOnGithubActionsMacOS Condition=" '$(IsGitHubActionsRunner)' == 'true' and '$(IsGithubPullRequest)' != 'true' ">true</RunOnGithubActionsMacOS>
+
     <!-- Timeout configuration -->
     <TestSessionTimeout>20m</TestSessionTimeout>
     <TestHangTimeout>15m</TestHangTimeout>