Mix wine, vinegar, olive oil, minced garlic and parsley in a baking dish. Add both fish fillets and top with chopped parsley. Let marinate for 2 hours.
Prepare two en papillote packets. Start by spooning 2 tbsp of marinate on the paper.Place fish on the paper. Arrange yellow and green peppers around the fish. Sprinkle on onions and garlic slices.
Top with a few spoonfuls of marinate mixture. Fold and seal the packet. Cook at 375 F (190 C) for 25-30 minutes.
Serve packet directly on a plate. Remember, half the fun of En Papillote is opening the packet!!! :-)