- In a bowl, combine oats, flour, brown sugar and cinnamon.Cut in butter with pastry blender till crumbly. Set aside.
- In a large mixing bowl, combine cake mix, eggs, water, butter and cinnamon. Beat on medium speed for 2 minutes.
- Spread batter evenly in prepared pan.
- Arrange apple slices evenly over batter.
- Sprinkle topping over apples.
- Bake for 40-45 minutes or until a tester inserted in center comes out clean.
- Cool completely in pan on wire rack.