In 4-quart Dutch oven, melt butter over medium heat. Cook celery, onion and mushrooms in butter about 3 minutes, stirring occasionally, until tender.
Stir in half of the croutons. Cook, stirring frequently, until evenly mixed and croutons are softened. Stir in remaining croutons and ingredients. Stuff turkey just before roasting. Or spoon stuffing into greased 3-quart casserole or 13x9-inch glass baking dish; cover and bake at 325°F for 30 minutes, then uncover and bake 15 minutes longer.