Foil Baked Flounder Fillets

Coat a skillet with cooking spray; add margarine. Melt margarine over medium heat. Add mushrooms and onion; sauté 5 minutes or until tender. Stir in next 3 ingredients; cook 5 minutes or until most of the liquid has evaporated.

Cut four 12-inch square pieces of heavy duty aluminum foil; place a filet, skin side down, in center of each piece of foil. Pepper each filet; top with one fourth of mushroom mixture.

Fold aluminum foil over fillets, and seal edges securely. Place foil packages on a baking sheet; bake at 400°F for 20 to 25 minutes or until fillets flake easily with a fork.