diff --git a/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/Module.java b/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/Module.java
index 61f44dc131d48e..1bd7020c609791 100644
--- a/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/Module.java
+++ b/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/Module.java
@@ -21,6 +21,7 @@
 import com.google.common.collect.Maps;
 import com.google.devtools.build.lib.cmdline.RepositoryMapping;
 import com.google.devtools.build.lib.cmdline.RepositoryName;
+import com.google.errorprone.annotations.CanIgnoreReturnValue;
 import java.util.Map;
 import java.util.function.UnaryOperator;
 import javax.annotation.Nullable;
@@ -138,9 +139,7 @@ public static Builder builder() {
         .setName("")
         .setVersion(Version.EMPTY)
         .setKey(ModuleKey.ROOT)
-        .setCompatibilityLevel(0)
-        .setExecutionPlatformsToRegister(ImmutableList.of())
-        .setToolchainsToRegister(ImmutableList.of());
+        .setCompatibilityLevel(0);
   }
 
   /**
@@ -168,11 +167,21 @@ public abstract static class Builder {
     /** Optional; defaults to {@code 0}. */
     public abstract Builder setCompatibilityLevel(int value);
 
-    /** Optional; defaults to an empty list. */
-    public abstract Builder setExecutionPlatformsToRegister(ImmutableList<String> value);
+    abstract ImmutableList.Builder<String> executionPlatformsToRegisterBuilder();
 
-    /** Optional; defaults to an empty list. */
-    public abstract Builder setToolchainsToRegister(ImmutableList<String> value);
+    @CanIgnoreReturnValue
+    public final Builder addExecutionPlatformsToRegister(Iterable<String> values) {
+      executionPlatformsToRegisterBuilder().addAll(values);
+      return this;
+    }
+
+    abstract ImmutableList.Builder<String> toolchainsToRegisterBuilder();
+
+    @CanIgnoreReturnValue
+    public final Builder addToolchainsToRegister(Iterable<String> values) {
+      toolchainsToRegisterBuilder().addAll(values);
+      return this;
+    }
 
     public abstract Builder setDeps(ImmutableMap<String, ModuleKey> value);
 
diff --git a/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/ModuleFileGlobals.java b/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/ModuleFileGlobals.java
index 4a0d44fc5b61b3..396ec6ccc7e525 100644
--- a/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/ModuleFileGlobals.java
+++ b/src/main/java/com/google/devtools/build/lib/bazel/bzlmod/ModuleFileGlobals.java
@@ -167,14 +167,16 @@ public void module(
     } catch (ParseException e) {
       throw new EvalException("Invalid version in module()", e);
     }
+    // TODO(wyv): migrate users of execution_platforms_to_register and toolchains_to_register to
+    // register_execution_platforms and register_toolchains, and remove the former two attributes.
     module
         .setName(name)
         .setVersion(parsedVersion)
         .setCompatibilityLevel(compatibilityLevel.toInt("compatibility_level"))
-        .setExecutionPlatformsToRegister(
+        .addExecutionPlatformsToRegister(
             checkAllAbsolutePatterns(
                 executionPlatformsToRegister, "execution_platforms_to_register"))
-        .setToolchainsToRegister(
+        .addToolchainsToRegister(
             checkAllAbsolutePatterns(toolchainsToRegister, "toolchains_to_register"));
     addRepoNameUsage(name, "as the current module name", thread.getCallerLocation());
   }
@@ -246,6 +248,40 @@ public void bazelDep(
     addRepoNameUsage(repoName, "by a bazel_dep", thread.getCallerLocation());
   }
 
+  @StarlarkMethod(
+      name = "register_execution_platforms",
+      doc =
+          "Specifies already-defined execution platforms to be registered when this module is"
+              + " selected. Should be absolute target patterns (ie. beginning with either"
+              + " <code>@</code> or <code>//</code>). See <a href=\"${link toolchains}\">toolchain"
+              + " resolution</a> for more information.",
+      extraPositionals =
+          @Param(
+              name = "platform_labels",
+              allowedTypes = {@ParamType(type = Sequence.class, generic1 = String.class)},
+              doc = "The labels of the platforms to register."))
+  public void registerExecutionPlatforms(Sequence<?> platformLabels) throws EvalException {
+    module.addExecutionPlatformsToRegister(
+        checkAllAbsolutePatterns(platformLabels, "register_execution_platforms"));
+  }
+
+  @StarlarkMethod(
+      name = "register_toolchains",
+      doc =
+          "Specifies already-defined toolchains to be registered when this module is selected."
+              + " Should be absolute target patterns (ie. beginning with either <code>@</code> or"
+              + " <code>//</code>). See <a href=\"${link toolchains}\">toolchain resolution</a> for"
+              + " more information.",
+      extraPositionals =
+          @Param(
+              name = "toolchain_labels",
+              allowedTypes = {@ParamType(type = Sequence.class, generic1 = String.class)},
+              doc = "The labels of the toolchains to register."))
+  public void registerToolchains(Sequence<?> toolchainLabels) throws EvalException {
+    module.addToolchainsToRegister(
+        checkAllAbsolutePatterns(toolchainLabels, "register_toolchains"));
+  }
+
   @StarlarkMethod(
       name = "use_extension",
       doc =
diff --git a/src/test/java/com/google/devtools/build/lib/bazel/bzlmod/ModuleFileFunctionTest.java b/src/test/java/com/google/devtools/build/lib/bazel/bzlmod/ModuleFileFunctionTest.java
index 223dfa6028df3f..deba48a57d85c3 100644
--- a/src/test/java/com/google/devtools/build/lib/bazel/bzlmod/ModuleFileFunctionTest.java
+++ b/src/test/java/com/google/devtools/build/lib/bazel/bzlmod/ModuleFileFunctionTest.java
@@ -183,6 +183,8 @@ public void testRootModule() throws Exception {
         ")",
         "bazel_dep(name='B',version='1.0')",
         "bazel_dep(name='C',version='2.0',repo_name='see')",
+        "register_toolchains('//my:toolchain3', '//my:toolchain4')",
+        "register_execution_platforms('//my:platform3', '//my:platform4')",
         "single_version_override(module_name='D',version='18')",
         "local_path_override(module_name='E',path='somewhere/else')",
         "multiple_version_override(module_name='F',versions=['1.0','2.0'])",
@@ -203,9 +205,12 @@ public void testRootModule() throws Exception {
                 .setVersion(Version.parse("0.1"))
                 .setKey(ModuleKey.ROOT)
                 .setCompatibilityLevel(4)
-                .setExecutionPlatformsToRegister(
-                    ImmutableList.of("//my:platform", "//my:platform2"))
-                .setToolchainsToRegister(ImmutableList.of("//my:toolchain", "//my:toolchain2"))
+                .addExecutionPlatformsToRegister(
+                    ImmutableList.of(
+                        "//my:platform", "//my:platform2", "//my:platform3", "//my:platform4"))
+                .addToolchainsToRegister(
+                    ImmutableList.of(
+                        "//my:toolchain", "//my:toolchain2", "//my:toolchain3", "//my:toolchain4"))
                 .addDep("B", createModuleKey("B", "1.0"))
                 .addDep("see", createModuleKey("C", "2.0"))
                 .build());