In a small skillet, saute celery and onion in butter until tender; transfer to a large bowl. Stir in the parsley, poultry seasoning, sage and pepper. Add bread cubes. Combine the egg, broth and oysters; add to bread mixture, stirring gently to combine.
Transfer to a greased 1-qt. baking dish. Cover and bake at 350° for 20 minutes. Uncover; bake 10-15 minutes longer or until a thermometer reads 160° and stuffing is lightly browned.