Reserve 1/2 cup cake mix for topping. Combine remaining cake mix, water, and egg substitute; stir just until dry ingredients are moistened. Fold in blueberries. Pour batter into a 9-inch square pan coated with cooking spray.
Combine reserved cake mix, brown sugar, and cinnamon; cut in margarine with a pastry blender until mixture resembles coarse meal. Sprinkle mixture over batter in pan. Bake at 375° for 27 to 30 minutes or until golden. Cut into squares; serve warm.