diff --git a/CHANGELOG.md b/CHANGELOG.md
index 33cb79c3a19..538353442bf 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,13 +7,13 @@
 - Save selectors dictionary to manifest, allow descriptions ([#2693](https://github.com/fishtown-analytics/dbt/issues/2693), [#2866](https://github.com/fishtown-analytics/dbt/pull/2866))
 - Normalize cli-style-strings in manifest selectors dictionary ([#2879](https://github.com/fishtown-anaytics/dbt/issues/2879), [#2895](https://github.com/fishtown-analytics/dbt/pull/2895))
 - Hourly, monthly and yearly partitions available in BigQuery ([#2476](https://github.com/fishtown-analytics/dbt/issues/2476), [#2903](https://github.com/fishtown-analytics/dbt/pull/2903))
+- Allow BigQuery to default to the environment's default project ([#2828](https://github.com/fishtown-analytics/dbt/pull/2828), [#2908](https://github.com/fishtown-analytics/dbt/pull/2908))
 
 ### Fixes
 - Respect --project-dir in dbt clean command ([#2840](https://github.com/fishtown-analytics/dbt/issues/2840), [#2841](https://github.com/fishtown-analytics/dbt/pull/2841))
 - Fix Redshift adapter `get_columns_in_relation` macro to push schema filter down to the `svv_external_columns` view ([#2855](https://github.com/fishtown-analytics/dbt/issues/2854))
 - Add `unixodbc-dev` package to testing docker image ([#2859](https://github.com/fishtown-analytics/dbt/pull/2859))
 - Increased the supported relation name length in postgres from 29 to 51 ([#2850](https://github.com/fishtown-analytics/dbt/pull/2850))
-- Widen supported Google Cloud libraries dependencies ([#2794](https://github.com/fishtown-analytics/dbt/pull/2794), [#2877](https://github.com/fishtown-analytics/dbt/pull/2877)).
 - dbt list command always return 0 as exit code ([#2886](https://github.com/fishtown-analytics/dbt/issues/2886), [#2892](https://github.com/fishtown-analytics/dbt/issues/2892))
 - Set default `materialized` for test node configs to `test` ([#2806](https://github.com/fishtown-analytics/dbt/issues/2806), [#2902](https://github.com/fishtown-analytics/dbt/pull/2902))
 
@@ -21,6 +21,7 @@
 - Bump hologram version to 0.0.11. Add scripts/dtr.py ([#2888](https://github.com/fishtown-analytics/dbt/issues/2840),[#2889](https://github.com/fishtown-analytics/dbt/pull/2889))
 - Add event tracking for project parser/load times ([#2823](https://github.com/fishtown-analytics/dbt/issues/2823),[#2893](https://github.com/fishtown-analytics/dbt/pull/2893))
 - Bump cryptography version to be >= 3.2 and bump snowflake connector to 2.3.6 ([#2896](https://github.com/fishtown-analytics/dbt/issues/2896))  
+- Widen supported Google Cloud libraries dependencies ([#2794](https://github.com/fishtown-analytics/dbt/pull/2794), [#2877](https://github.com/fishtown-analytics/dbt/pull/2877)).
 
 Contributors:
 - [@feluelle](https://github.com/feluelle) ([#2841](https://github.com/fishtown-analytics/dbt/pull/2841))
@@ -29,7 +30,7 @@ Contributors:
 - [@brangisom](https://github.com/brangisom) [#2855](https://github.com/fishtown-analytics/dbt/pull/2855)
 - [@elexisvenator](https://github.com/elexisvenator) ([#2850](https://github.com/fishtown-analytics/dbt/pull/2850))
 - [@franloza](https://github.com/franloza) ([#2837](https://github.com/fishtown-analytics/dbt/pull/2837))
-- [@max-sixty](https://github.com/max-sixty) ([#2877](https://github.com/fishtown-analytics/dbt/pull/2877))
+- [@max-sixty](https://github.com/max-sixty) ([#2877](https://github.com/fishtown-analytics/dbt/pull/2877), [#2908](https://github.com/fishtown-analytics/dbt/pull/2908))
 - [@rsella](https://github.com/rsella) ([#2892](https://github.com/fishtown-analytics/dbt/issues/2892))
 - [@plotneishestvo](https://github.com/plotneishestvo) ([#2896](https://github.com/fishtown-analytics/dbt/issues/2896))
 - [@db-magnus](https://github.com/db-magnus) ([#2892](https://github.com/fishtown-analytics/dbt/issues/2892))
diff --git a/plugins/bigquery/dbt/adapters/bigquery/connections.py b/plugins/bigquery/dbt/adapters/bigquery/connections.py
index 738935d3e23..743718869cd 100644
--- a/plugins/bigquery/dbt/adapters/bigquery/connections.py
+++ b/plugins/bigquery/dbt/adapters/bigquery/connections.py
@@ -1,7 +1,8 @@
 from contextlib import contextmanager
 from dataclasses import dataclass
+from functools import lru_cache
 from requests.exceptions import ConnectionError
-from typing import Optional, Any, Dict
+from typing import Optional, Any, Dict, Tuple
 
 import google.auth
 import google.auth.exceptions
@@ -45,6 +46,17 @@
 )
 
 
+@lru_cache()
+def get_bigquery_defaults() -> Tuple[Any, Optional[str]]:
+    """
+    Returns (credentials, project_id)
+
+    project_id is returned available from the environment; otherwise None
+    """
+    # Cached, because the underlying implementation shells out, taking ~1s
+    return google.auth.default()
+
+
 class Priority(StrEnum):
     Interactive = 'interactive'
     Batch = 'batch'
@@ -60,6 +72,9 @@ class BigQueryConnectionMethod(StrEnum):
 @dataclass
 class BigQueryCredentials(Credentials):
     method: BigQueryConnectionMethod
+    # BigQuery allows an empty database / project, where it defers to the
+    # environment for the project
+    database: Optional[str]
     timeout_seconds: Optional[int] = 300
     location: Optional[str] = None
     priority: Optional[Priority] = None
@@ -91,6 +106,16 @@ def _connection_keys(self):
         return ('method', 'database', 'schema', 'location', 'priority',
                 'timeout_seconds', 'maximum_bytes_billed')
 
+    def __post_init__(self):
+        # We need to inject the correct value of the database (aka project) at
+        # this stage, ref
+        # https://github.com/fishtown-analytics/dbt/pull/2908#discussion_r532927436.
+
+        # `database` is an alias of `project` in BigQuery
+        if self.database is None:
+            _, database = get_bigquery_defaults()
+            self.database = database
+
 
 class BigQueryConnectionManager(BaseConnectionManager):
     TYPE = 'bigquery'
@@ -170,7 +195,7 @@ def get_bigquery_credentials(cls, profile_credentials):
         creds = GoogleServiceAccountCredentials.Credentials
 
         if method == BigQueryConnectionMethod.OAUTH:
-            credentials, project_id = google.auth.default(scopes=cls.SCOPE)
+            credentials, _ = get_bigquery_defaults()
             return credentials
 
         elif method == BigQueryConnectionMethod.SERVICE_ACCOUNT:
diff --git a/test/unit/test_bigquery_adapter.py b/test/unit/test_bigquery_adapter.py
index 1232ced021b..0380c7e095e 100644
--- a/test/unit/test_bigquery_adapter.py
+++ b/test/unit/test_bigquery_adapter.py
@@ -96,6 +96,13 @@ def setUp(self):
                     'priority': 'batch',
                     'maximum_bytes_billed': 0,
                 },
+                'oauth--no-project': {
+                    'type': 'bigquery',
+                    'method': 'oauth',
+                    'schema': 'dummy_schema',
+                    'threads': 1,
+                    'location': 'Solar Station',
+                },
             },
             'target': 'oauth',
         }