Generously grease a 9-inch square baking dish. In a small bowl, combine brown sugar and cinnamon and mix well with a fork. Separate biscuit dough into 10 biscuits. Cut each biscuit into quarters, and dip each piece in melted butter and coat with brown sugar mixture. Arrange in a single layer in baking dish. Sprinkle with 1/2 cup of the oats.
Combine blueberries and sugar in a bowl and toss to coat. Spoon over oats and biscuits and sprinkle with remaining 1/2 cup oats. Drizzle remaining melted butter on top. Bake for 20 minutes or until cake is golden brown and center is done. Cool for 20 minutes. Serve warm.