Stir together cereal and butter; spoon half of cereal mixture into a lightly greased 11- x 7-inch baking dish. Top with cabbage and onion.
Stir together milk, mayonnaise, and soup; pour over cabbage. Sprinkle with cheese and remaining cereal mixture.
Bake, covered, at 350° for 1 hour.
Note: To lighten this recipe, use light butter, fat-free milk, reduced-fat mayonnaise, reduced-fat soup and reduced fat-cheese.