In a large skillet, saute the onions, celery and mushrooms in butter until tender. Add broth and seasonings; mix well. Place bread cubes in a large bowl; add mushroom mixture and toss to coat. Stir in enough warm water to reach desired moistness. , Just before baking, loosely stuff turkey. Place any remaining stuffing in a greased baking dish; cover and refrigerated until ready to bake. Skewer turkey openings; tie drumsticks together with kitchen string. Place breast side up on a rack in a roasting pan. Brush with melted butter., Bake turkey, uncovered, at 325° for 3-3/4 to 4-1/2 hours or until a thermometer reads 180° for the turkey and 165° for the stuffing, basting occasionally with pan drippings. (Cover loosely with foil if turkey browns too quickly.), Bake additional stuffing, covered, for 30-40 minutes. Uncover; bake 10 minutes longer or until lightly browned. Cover turkey with foil and let stand for 20 minutes before removing stuffing and carving. If desired, thicken pan drippings for gravy.