diff --git a/firestore-bigquery-export/firestore-bigquery-change-tracker/src/__tests__/bigquery/gcpProject.test.ts b/firestore-bigquery-export/firestore-bigquery-change-tracker/src/__tests__/bigquery/gcpProject.test.ts
new file mode 100644
index 000000000..01c153378
--- /dev/null
+++ b/firestore-bigquery-export/firestore-bigquery-change-tracker/src/__tests__/bigquery/gcpProject.test.ts
@@ -0,0 +1,50 @@
+/*
+ * Copyright 2019 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { resolveGcpProjectIdForBigQuery } from "../../bigquery/gcpProject";
+
+const ENV_VARS = ["PROJECT_ID", "GOOGLE_CLOUD_PROJECT"];
+
+function clearEnv() {
+  for (const v of ENV_VARS) delete process.env[v];
+}
+
+beforeEach(clearEnv);
+afterEach(clearEnv);
+
+describe("resolveGcpProjectIdForBigQuery", () => {
+  it("returns the explicit preferred value first", () => {
+    process.env.GOOGLE_CLOUD_PROJECT = "env-project";
+    expect(resolveGcpProjectIdForBigQuery("explicit-project")).toBe(
+      "explicit-project"
+    );
+  });
+
+  it("prefers GOOGLE_CLOUD_PROJECT over PROJECT_ID (Gen2 / Cloud Run)", () => {
+    process.env.GOOGLE_CLOUD_PROJECT = "gen2-project";
+    process.env.PROJECT_ID = "gen1-project";
+    expect(resolveGcpProjectIdForBigQuery(undefined)).toBe("gen2-project");
+  });
+
+  it("falls back to PROJECT_ID when GOOGLE_CLOUD_PROJECT is absent", () => {
+    process.env.PROJECT_ID = "gen1-project";
+    expect(resolveGcpProjectIdForBigQuery(undefined)).toBe("gen1-project");
+  });
+
+  it("returns undefined when no source is available", () => {
+    expect(resolveGcpProjectIdForBigQuery(undefined)).toBeUndefined();
+  });
+});
diff --git a/firestore-bigquery-export/firestore-bigquery-change-tracker/src/bigquery/gcpProject.ts b/firestore-bigquery-export/firestore-bigquery-change-tracker/src/bigquery/gcpProject.ts
new file mode 100644
index 000000000..7c23866ef
--- /dev/null
+++ b/firestore-bigquery-export/firestore-bigquery-change-tracker/src/bigquery/gcpProject.ts
@@ -0,0 +1,25 @@
+/*
+ * Copyright 2019 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+export function resolveGcpProjectIdForBigQuery(
+  preferred?: string
+): string | undefined {
+  return (
+    preferred ||
+    process.env.GOOGLE_CLOUD_PROJECT ||
+    process.env.PROJECT_ID
+  );
+}
diff --git a/firestore-bigquery-export/firestore-bigquery-change-tracker/src/bigquery/index.ts b/firestore-bigquery-export/firestore-bigquery-change-tracker/src/bigquery/index.ts
index 7b6f8a15e..ef9627f54 100644
--- a/firestore-bigquery-export/firestore-bigquery-change-tracker/src/bigquery/index.ts
+++ b/firestore-bigquery-export/firestore-bigquery-change-tracker/src/bigquery/index.ts
@@ -42,6 +42,7 @@ import { tableRequiresUpdate } from "./checkUpdates";
 import { parseErrorMessage, waitForInitialization } from "./utils";
 import { initializeLatestView } from "./initializeLatestView";
 import { logger, LogLevel } from "../logger";
+import { resolveGcpProjectIdForBigQuery } from "./gcpProject";
 
 export { RawChangelogSchema, RawChangelogViewSchema } from "./schema";
 import type { ChangeTrackerConfig } from "./types";
@@ -68,7 +69,7 @@ export class FirestoreBigQueryEventHistoryTracker
   constructor(public config: ChangeTrackerConfig) {
     this.bq = new bigquery.BigQuery();
 
-    this.bq.projectId = config.bqProjectId || process.env.PROJECT_ID;
+    this.bq.projectId = resolveGcpProjectIdForBigQuery(config.bqProjectId);
 
     this.partitioningConfig = new PartitioningConfig(this.config.partitioning);
 
diff --git a/firestore-bigquery-export/firestore-bigquery-change-tracker/src/bigquery/snapshot.ts b/firestore-bigquery-export/firestore-bigquery-change-tracker/src/bigquery/snapshot.ts
index 01d2bee62..7e5fd69e0 100644
--- a/firestore-bigquery-export/firestore-bigquery-change-tracker/src/bigquery/snapshot.ts
+++ b/firestore-bigquery-export/firestore-bigquery-change-tracker/src/bigquery/snapshot.ts
@@ -16,6 +16,7 @@
 
 import * as sqlFormatter from "sql-formatter";
 import { timestampField } from "./schema";
+import { resolveGcpProjectIdForBigQuery } from "./gcpProject";
 
 const excludeFields: string[] = ["document_name", "document_id"];
 const nonGroupFields = ["event_id", "data", "old_data"];
@@ -65,7 +66,12 @@ export function buildLatestSnapshotViewQuery({
 }: BuildLatestSnapshotViewQueryOptions): string {
   validateInputs({ datasetId, tableName, timestampColumnName, groupByColumns });
 
-  const projectId = bqProjectId || process.env.PROJECT_ID;
+  const projectId = resolveGcpProjectIdForBigQuery(bqProjectId);
+  if (!projectId) {
+    throw new Error(
+      "Could not determine BigQuery project ID. Provide it via the bqProjectId config option or set the GOOGLE_CLOUD_PROJECT / PROJECT_ID environment variable."
+    );
+  }
 
   return useLegacyQuery
     ? buildLegacyQuery(