Preheat oven to 325 degrees. Spray a 13x9" pan with butter flavored cooking spray and wipe with a paper towel. In a medium sized bowl, combine flour, baking powder, salt, cinnamon, and oats and mix well. In a large bowl, combine sugar, mil, and margarine and mix well. Add dry mixture to wet mixture and mix well. Pour batter into pan. Bake for 30 minutes. Meanwhile, make topping. Thoroughly stir together topping ingredients. Spread topping over warm cake. 15 servings. Fat less than .5 g.