diff --git a/dataconnect/models.py b/dataconnect/models.py
index af696a5..57f67b0 100644
--- a/dataconnect/models.py
+++ b/dataconnect/models.py
@@ -14,6 +14,7 @@
 class StudyEnvironment:
     uuid: UUID
     name: str
+    oid: str | None = None
 
 
 @dataclass(frozen=True)
diff --git a/dataconnect/service/mappers.py b/dataconnect/service/mappers.py
index 66bae58..e1c705e 100644
--- a/dataconnect/service/mappers.py
+++ b/dataconnect/service/mappers.py
@@ -53,7 +53,10 @@ def resource_to_study(resource: ResourceInfo) -> Study:
     return Study(
         uuid=UUID(data["uuid"]),
         name=data["name"],
-        environments=[StudyEnvironment(uuid=UUID(e["uuid"]), name=e["name"]) for e in data.get("environments", [])],
+        environments=[
+            StudyEnvironment(uuid=UUID(e["uuid"]), name=e["name"], oid=e.get("oid"))
+            for e in data.get("environments", [])
+        ],
     )
 
 
diff --git a/readme/README-v1.1.0.md b/readme/README-v1.1.0.md
index 69c18d2..fd70545 100644
--- a/readme/README-v1.1.0.md
+++ b/readme/README-v1.1.0.md
@@ -127,7 +127,7 @@ Retrieves a list of studies where the user has permission to manage custom code
 | search_study_name | str or None | Optional. The approximate name of the study |
 
 #### Output
-Returns a list containing `total_records` (total studies available) and a `studies` array. Each study includes `name`, `uuid`, and an environments array. Each environment includes `name` and `uuid`.
+Returns a list containing `total_records` (total studies available) and a `studies` array. Each study includes `name`, `uuid`, and an environments array. Each environment includes `name`, `uuid`, and `oid` — the upstream study environment OID.
 
 ---
 
diff --git a/tests/test_resource_to_study.py b/tests/test_resource_to_study.py
new file mode 100644
index 0000000..9eead2a
--- /dev/null
+++ b/tests/test_resource_to_study.py
@@ -0,0 +1,67 @@
+from __future__ import annotations
+
+import json
+from uuid import UUID
+
+from dataconnect.service.mappers import resource_to_study
+from dataconnect.transport.models import DataRef, ResourceInfo
+
+
+def _resource(payload: dict) -> ResourceInfo:
+    return ResourceInfo(
+        descriptor=b"",
+        endpoints=[DataRef(ticket=json.dumps(payload).encode("utf-8"))],
+        total_records=1,
+        schema_bytes=b"",
+    )
+
+
+def test_resource_to_study_exposes_environment_oid() -> None:
+    resource = _resource(
+        {
+            "uuid": "12345678-1234-1234-1234-123456789abc",
+            "name": "Study A",
+            "environments": [{"uuid": "11111111-1111-1111-1111-111111111111", "name": "Production", "oid": "prod"}],
+        }
+    )
+
+    study = resource_to_study(resource)
+
+    assert study.environments[0].oid == "prod"
+    assert study.environments[0].name == "Production"
+    assert study.environments[0].uuid == UUID("11111111-1111-1111-1111-111111111111")
+
+
+def test_resource_to_study_oid_differs_from_name_multiple_environments() -> None:
+    resource = _resource(
+        {
+            "uuid": "12345678-1234-1234-1234-123456789abc",
+            "name": "Study A",
+            "environments": [
+                {"uuid": "11111111-1111-1111-1111-111111111111", "name": "Production", "oid": "prod"},
+                {"uuid": "22222222-2222-2222-2222-222222222222", "name": "Custom Env", "oid": "other"},
+            ],
+        }
+    )
+
+    study = resource_to_study(resource)
+
+    # OID must track its own environment, not be derived from name/uuid.
+    assert study.environments[0].oid == "prod"
+    assert study.environments[1].oid == "other"
+    assert study.environments[1].name == "Custom Env"
+
+
+def test_resource_to_study_missing_oid_defaults_to_none() -> None:
+    """Older/partial server payloads without 'oid' must not break parsing."""
+    resource = _resource(
+        {
+            "uuid": "12345678-1234-1234-1234-123456789abc",
+            "name": "Study A",
+            "environments": [{"uuid": "11111111-1111-1111-1111-111111111111", "name": "Production"}],
+        }
+    )
+
+    study = resource_to_study(resource)
+
+    assert study.environments[0].oid is None