Melt margarine in large saucepan on medium heat. Whisk in flour; cook 1 min., stirring constantly. Gradually stir in milk; cook and stir 3 to 5 min. or until thickened. Add Parmesan and 1-1/2 cups cheddar; cook and stir 1 min. or until cheddar is melted. Add macaroni; stir to evenly coat.