PREHEAT oven to 350°F. Melt butter in large saucepan on low heat. Stir in flour. Cook 2 min., stirring constantly. Gradually add milk, stirring until well blended. Cook until thickened, stirring constantly. Stir in 1 cup of the mozzarella cheese and 1/4 cup of the Parmesan cheese; stir until mozzarella cheese is melted. Add spaghetti, chicken, mushrooms and peppers; mix lightly.
SPOON into 1-1/2-qt. baking dish.
BAKE 20 min. Top with the remaining mozzarella and Parmesan cheeses; continue baking until mozzarella cheese is melted.
KRAFT KITCHENS TIPS
Serve with a mixed green salad for added color and texture.
Substitute chopped cooked turkey for the chicken.
RECIPE COURTESY OF KRAFT FOODS