1Cook and drain pasta as directed on package.
2While pasta is cooking, melt margarine in 3-quart saucepan over medium heat. Cook chicken, mushrooms, onions and garlic in margarine about 5 minutes, stirring occasionally, until chicken is no longer pink in center.
3Stir in flour, thyme and pepper. Cook over medium heat, stirring constantly, until mixture is smooth and bubbly; remove from heat. Gradually stir in milk. Heat to boiling, stirring constantly. Boil and stir 1 minute. Stir in cheese until melted.
4Pour chicken mixture over pasta; toss if desired.