diff --git a/docetl/operations/reduce.py b/docetl/operations/reduce.py
index cf3afae3..a5086606 100644
--- a/docetl/operations/reduce.py
+++ b/docetl/operations/reduce.py
@@ -253,19 +253,23 @@ def execute(self, input_data: List[Dict]) -> Tuple[List[Dict], float]:
             reduce_keys = [reduce_keys]
         input_schema = self.config.get("input", {}).get("schema", {})
 
-        # Group the input data by the reduce key(s) while maintaining original order
-        def get_group_key(item):
-            return tuple(item[key] for key in reduce_keys)
-
-        grouped_data = {}
-        for item in input_data:
-            key = get_group_key(item)
-            if key not in grouped_data:
-                grouped_data[key] = []
-            grouped_data[key].append(item)
-
-        # Convert the grouped data to a list of tuples
-        grouped_data = list(grouped_data.items())
+        # Check if we need to group everything into one group
+        if reduce_keys == ["_all"] or reduce_keys == "_all":
+            grouped_data = [("_all", input_data)]
+        else:
+            # Group the input data by the reduce key(s) while maintaining original order
+            def get_group_key(item):
+                return tuple(item[key] for key in reduce_keys)
+
+            grouped_data = {}
+            for item in input_data:
+                key = get_group_key(item)
+                if key not in grouped_data:
+                    grouped_data[key] = []
+                grouped_data[key].append(item)
+
+            # Convert the grouped data to a list of tuples
+            grouped_data = list(grouped_data.items())
 
         def process_group(
             key: Tuple, group_elems: List[Dict]
diff --git a/tests/test_basic.py b/tests/test_basic.py
index ed5b216b..7d1bf6b4 100644
--- a/tests/test_basic.py
+++ b/tests/test_basic.py
@@ -488,6 +488,17 @@ def test_reduce_operation(
     assert cost > 0
 
 
+def test_reduce_operation_with_all_key(
+    reduce_config, default_model, max_threads, reduce_sample_data
+):
+    reduce_config["reduce_key"] = "_all"
+    operation = ReduceOperation(reduce_config, default_model, max_threads)
+    results, cost = operation.execute(reduce_sample_data)
+
+    assert len(results) == 1
+    assert cost > 0
+
+
 def test_reduce_operation_with_list_key(
     reduce_config, default_model, max_threads, reduce_sample_data_with_list_key
 ):