HEAT oven to 350°F.
TOSS spaghetti with 3 Tbsp. Parmesan and the egg whites. Place in 9-inch pie plate; press onto bottom and up side to form crust.
BROWN meat with peppers in large nonstick skillet on medium-high heat. Stir in spaghetti sauce; simmer 5 min. Spoon into spaghetti crust; top with mozzarella and remaining Parmesan.
BAKE 25 min. or until heated through. Cut into wedges to serve.