Sauté celery in 1/4 cup butter until tender.
Combine stuffing mix, parsley, sautéed celery, salt, and pepper; stir well.
Layer half of oysters in a lightly greased 12- x 8- x 2-inch baking dish; top with half of stuffing mixture. Repeat layers; pour remaining butter over mixture in baking dish. Bake at 350° for 30 minutes or until bubbly.