Combine first 6 ingredients in a large bowl; cut in butter with a pastry blender until mixture is crumbly and begins to stick together.
Combine granulated sugar and flour. Toss together granulated sugar mixture, blueberries, and lemon juice in a medium bowl. Transfer blueberry mixture to a lightly greased 2-quart baking dish. Sprinkle oat mixture evenly over blueberry mixture.
Bake at 350° for 50 minutes or until bubbly and golden.
Note: For testing purposes only, we used Bisquick Heart Smart All-Purpose Baking Mix.