Cook onions in margarine in large nonstick skillet on medium heat 8 min. or until tender, stirring frequently. Blend in flour; cook and stir 1 min. Gradually stir in broth; cook 5 min. or until thickened, stirring constantly. Add 1 cup shredded cheese and pepper; cook and stir 1 min. or until cheese is melted. Remove from heat.