Sauté onions and celery in 2 tbsp. of the butter until softened.Combine cornbread and bread crumbs in a large bowl; mix in onions, celery, salt and pepper, and parsley. Add beaten eggs and toss once more. Moisten with the oyster liquid until moist but not soggy. Add the oysters.
Pat the mixture into a lightly buttered rectangular cake pan to about 1-inch deep. Dot with remaining 2 tbsp. butter and bake for 45 minutes, until set and golden brown.
