HEAT oven to 400ºF.
DIP chicken in egg whites, then in bread crumbs, turning to evenly coat both sides of each breast. Place in 13x9-inch pan sprayed with cooking spray.
BAKE 20 to 25 min. or until chicken is done (165ºF). Top with 2 cups sauce, cheeses and oregano. Bake 5 min. or until mozzarella is melted. Meanwhile, heat remaining sauce.
TOSS spaghetti with sauce; place on plate. Top with chicken.