Place onions and parsley in oil and sauté 3 to 5 minutes. Add garlic and then the rest of the ingredients, except catfish fillets. Cook until the onions are translucent, about 10 minutes. On medium-hot grill place fillets, skin side up, for 3 minutes. Turn and cook 2 minutes more. Place in aluminum foil "boat" or grill-safe pan on grill; top with sauce. Close top on grill and cook 10 minutes.