COOK pasta as directed on package; drain. Set aside.
MEANWHILE, spray large skillet with cooking spray. Add chicken; cook on medium heat 5 min., stirring occasionally. Add peppers and onions; cook 3 to 5 min. or until chicken is cooked through and vegetables are crisp-tender, stirring occasionally.
ADD spaghetti sauce and pasta; mix well. Cook until heated through, stirring occasionally. Top with cheese; cover. Let stand 2 to 3 min. or until cheese is melted.