Halibut in Parchment Paper

2 halibut fillets (6 to 8 oz ea) 2 tablespoons butter 2 teaspoons chopped fresh parsley 1/2 red onion , finely sliced 1 zucchini , finely sliced 1 yellow[...]

24 ounces halibut, cut into 4 equal pieces (any firm white fish will do such as cod or flounder) salt and freshly ground black pepper 1 summer squash (yellow)[...]