BROWN meat in large nonstick skillet on medium-high heat; drain. reserving meat in skillet.
STIR in Macaroni, Cheese Sauce, tomatoes, peas and milk. Bring to boil; cover. Simmer on medium-low 12 min. or until macaroni is tender, stirring occasionally.
TOP with mozzarella. Let stand, covered, 5 min. or until melted.