Onion Potatoes

1 hr. before serving: In small saucepan over medium heat, melt 1/2 c. butter; stir in 1 env. onion soup mix for 4 servings until blended. With sharp knife, quarter 6 med. all purpose potatoes; place each potato on large sheet of heavy duty foil. Spoon onion mixture between cut quarters; fold foil over and wrap securely. Bake on cookie sheet 45 min. or until fork tender. Serve from foil package. 6 servings.