Pre-heat oven to 375°F.
Spray a 9-inch pan with non-stick spray.
In a separate bowl, mix together flour, oatmeal, brown sugar, and cinnamon. Add butter and mix with a fork or pastry blender to form a coarse meal.
Toss half of mixture over sliced apples and add to baking pan. Pour small amount of water in each corner of pan. Cover with foil and bake 25-30 minutes. Remove foil, pour remaining oatmeal mixture over top and bake for 10 minutes.
Makes 10 servings: 180 calories, 5 grams fat