In skillet, in 1 tablespoon hot margarine, cook chicken 10 minutes or until browned on both sides.
Remove.
In remaining 1 tablespoon hot margarine, cook mushrooms and onion with garlic powder until tender and liquid is evaporated (stirring often). Add remaining ingredients.
Heat to boiling.
Return chicken to skillet.
Cover; cook over low heat 5 minutes or until chicken is no longer pink, stirring occasionally.