Sharp Cheddar "Lasagna"

1 pkg. (14 oz.) KRAFT Deluxe Macaroni & Sharp Cheddar Cheese Sauce
1 lb. ground beef
1 jar (14 oz.) spaghetti sauce (about 1-1/2 cups)
1/2 cup KRAFT Shredded Mozzarella Cheese
1 small onion (chopped)

PREHEAT oven to 375°F. Prepare Dinner as directed on package. Meanwhile, brown meat and onion in large skillet; drain. Add spaghetti sauce to meat; mix well.
LAYER half each of the meat mixture and prepared Dinner in 8-inch square baking dish. Repeat layers. Sprinkle with mozzarella cheese.
BAKE 15 min. or until heated through.