Spoon apple slices into an 8-inch square pan; sprinkle with orange rind and juice.
Combine oats and next 5 ingredients in a medium bowl; stir well. Cut in margarine with a pastry blender until mixture resembles coarse meal. Sprinkle mixture over apple. Bake at 375° for 40 to 45 minutes or until apple is tender and topping is lightly browned. Spoon into individual dessert bowls; top each serving with 1 tablespoon whipped topping.