Prepare as directed except for baking; cover. Refrigerate up to 24 hours. When ready to serve, bake, covered, at 375°F for 40 to 45 min. or until heated through. Remove from oven; uncover. Sprinkle with remaining 1/2 cup cheese. Let stand 5 min. or until cheese is melted.
Substitute 2 cans (170 g each) solid white tuna packed in water, drained, for the cooked ground beef.