diff --git a/.changeset/modern-snails-judge.md b/.changeset/modern-snails-judge.md
new file mode 100644
index 00000000..0992746d
--- /dev/null
+++ b/.changeset/modern-snails-judge.md
@@ -0,0 +1,6 @@
+---
+'@apollo/explorer': minor
+'@apollo/sandbox': minor
+---
+
+Support Explorer preflight OAuth in embeds
diff --git a/packages/explorer/src/helpers/constants.ts b/packages/explorer/src/helpers/constants.ts
index a4d25c46..424cc075 100644
--- a/packages/explorer/src/helpers/constants.ts
+++ b/packages/explorer/src/helpers/constants.ts
@@ -33,5 +33,9 @@ export const EXPLORER_LISTENING_FOR_PARTIAL_TOKEN =
   'ExplorerListeningForPartialToken';
 export const PARTIAL_AUTHENTICATION_TOKEN_RESPONSE =
   'PartialAuthenticationTokenResponse';
+export const PREFLIGHT_OAUTH_REQUEST = 'PreflightOAuthRequest';
+export const PREFLIGHT_OAUTH_PROVIDER_RESPONSE =
+  'PreflightOAuthProviderResponse';
+export const PREFLIGHT_OAUTH_RESPONSE = 'PreflightOAuthResponse';
 export const INTROSPECTION_QUERY_WITH_HEADERS = 'IntrospectionQueryWithHeaders';
 export const PARENT_LOGOUT_SUCCESS = 'ParentLogoutSuccess';
diff --git a/packages/explorer/src/helpers/postMessageRelayHelpers.ts b/packages/explorer/src/helpers/postMessageRelayHelpers.ts
index 58d25f3f..7ebe52a4 100644
--- a/packages/explorer/src/helpers/postMessageRelayHelpers.ts
+++ b/packages/explorer/src/helpers/postMessageRelayHelpers.ts
@@ -21,6 +21,9 @@ import {
   EXPLORER_SUBSCRIPTION_REQUEST,
   EXPLORER_SUBSCRIPTION_TERMINATION,
   EXPLORER_LISTENING_FOR_SCHEMA,
+  PREFLIGHT_OAUTH_REQUEST,
+  PREFLIGHT_OAUTH_PROVIDER_RESPONSE,
+  PREFLIGHT_OAUTH_RESPONSE,
 } from './constants';
 import MIMEType from 'whatwg-mimetype';
 import { readMultipartWebStream } from './readMultipartWebStream';
@@ -159,9 +162,21 @@ export type OutgoingEmbedMessage =
     }
   | {
       name: typeof PARENT_LOGOUT_SUCCESS;
+    }
+  | {
+      name: typeof PREFLIGHT_OAUTH_RESPONSE;
+      queryParams: string;
     };
 
 export type IncomingEmbedMessage =
+  | MessageEvent<{
+      name: typeof PREFLIGHT_OAUTH_REQUEST;
+      oauthUrl: string;
+    }>
+  | MessageEvent<{
+      name: typeof PREFLIGHT_OAUTH_PROVIDER_RESPONSE;
+      queryParams: string;
+    }>
   | MessageEvent<{
       name: typeof EXPLORER_LISTENING_FOR_HANDSHAKE;
     }>
@@ -504,6 +519,23 @@ export const handleAuthenticationPostMessage = ({
   embedUrl: string;
 }) => {
   const { data } = event;
+  if (data.name === PREFLIGHT_OAUTH_REQUEST) {
+    const handleEmbedPostMessage = (event: IncomingEmbedMessage) => {
+      if (event.data.name === PREFLIGHT_OAUTH_PROVIDER_RESPONSE) {
+        window.removeEventListener('message', handleEmbedPostMessage);
+        sendPostMessageToEmbed({
+          message: {
+            name: PREFLIGHT_OAUTH_RESPONSE,
+            queryParams: event.data.queryParams,
+          },
+          embeddedIFrameElement,
+          embedUrl,
+        });
+      }
+    };
+    window.addEventListener('message', handleEmbedPostMessage);
+    window.open(data.oauthUrl, undefined, '_blank');
+  }
   // When the embed authenticates, save the partial token in local storage
   if (data.name === SET_PARTIAL_AUTHENTICATION_TOKEN_FOR_PARENT) {
     const partialEmbedApiKeysString = window.localStorage.getItem(
diff --git a/packages/sandbox/src/helpers/constants.ts b/packages/sandbox/src/helpers/constants.ts
index 91f069bd..c80876db 100644
--- a/packages/sandbox/src/helpers/constants.ts
+++ b/packages/sandbox/src/helpers/constants.ts
@@ -34,5 +34,9 @@ export const EXPLORER_LISTENING_FOR_PARTIAL_TOKEN =
   'ExplorerListeningForPartialToken';
 export const PARTIAL_AUTHENTICATION_TOKEN_RESPONSE =
   'PartialAuthenticationTokenResponse';
+export const PREFLIGHT_OAUTH_REQUEST = 'PreflightOAuthRequest';
+export const PREFLIGHT_OAUTH_PROVIDER_RESPONSE =
+  'PreflightOAuthProviderResponse';
+export const PREFLIGHT_OAUTH_RESPONSE = 'PreflightOAuthResponse';
 export const INTROSPECTION_QUERY_WITH_HEADERS = 'IntrospectionQueryWithHeaders';
 export const PARENT_LOGOUT_SUCCESS = 'ParentLogoutSuccess';
diff --git a/packages/sandbox/src/helpers/postMessageRelayHelpers.ts b/packages/sandbox/src/helpers/postMessageRelayHelpers.ts
index 8bbba65e..3cac55ba 100644
--- a/packages/sandbox/src/helpers/postMessageRelayHelpers.ts
+++ b/packages/sandbox/src/helpers/postMessageRelayHelpers.ts
@@ -23,6 +23,9 @@ import {
   EXPLORER_SUBSCRIPTION_TERMINATION,
   EXPLORER_LISTENING_FOR_SCHEMA,
   INTROSPECTION_QUERY_WITH_HEADERS,
+  PREFLIGHT_OAUTH_REQUEST,
+  PREFLIGHT_OAUTH_RESPONSE,
+  PREFLIGHT_OAUTH_PROVIDER_RESPONSE,
 } from './constants';
 import MIMEType from 'whatwg-mimetype';
 import { readMultipartWebStream } from './readMultipartWebStream';
@@ -168,9 +171,21 @@ export type OutgoingEmbedMessage =
     }
   | {
       name: typeof PARENT_LOGOUT_SUCCESS;
+    }
+  | {
+      name: typeof PREFLIGHT_OAUTH_RESPONSE;
+      queryParams: string;
     };
 
 export type IncomingEmbedMessage =
+  | MessageEvent<{
+      name: typeof PREFLIGHT_OAUTH_REQUEST;
+      oauthUrl: string;
+    }>
+  | MessageEvent<{
+      name: typeof PREFLIGHT_OAUTH_PROVIDER_RESPONSE;
+      queryParams: string;
+    }>
   | MessageEvent<{
       name: typeof EXPLORER_LISTENING_FOR_HANDSHAKE;
     }>
@@ -588,6 +603,23 @@ export const handleAuthenticationPostMessage = ({
   embedUrl: string;
 }) => {
   const { data } = event;
+  if (data.name === PREFLIGHT_OAUTH_REQUEST) {
+    const handleEmbedPostMessage = (event: IncomingEmbedMessage) => {
+      if (event.data.name === PREFLIGHT_OAUTH_PROVIDER_RESPONSE) {
+        window.removeEventListener('message', handleEmbedPostMessage);
+        sendPostMessageToEmbed({
+          message: {
+            name: PREFLIGHT_OAUTH_RESPONSE,
+            queryParams: event.data.queryParams,
+          },
+          embeddedIFrameElement,
+          embedUrl,
+        });
+      }
+    };
+    window.addEventListener('message', handleEmbedPostMessage);
+    window.open(data.oauthUrl, undefined, '_blank');
+  }
   // When the embed authenticates, save the partial token in local storage
   if (data.name === SET_PARTIAL_AUTHENTICATION_TOKEN_FOR_PARENT) {
     const partialEmbedApiKeysString = window.localStorage.getItem(