Peel apples and slice thin. Arrange in square baking dish about 10- by 6-inches. Sprinkle with cinnamon. Spoon cranberry sauce over this. Stir rolled oats (oatmeal), flour, and brown sugar together. Cut in butter until evenly mixed and crumbly. Sprinkle this over cranberry layer. Bake in moderate oven (350 degrees) until apples are cooked through and top is lightly browned. About 40 minutes. Good served plain or with whipped cream or vanilla ice cream. Serve hot.