Sauté vegetables in butter until tender-crisp. Stir in seasonings.
Combine breads in a large bowl; add vegetable mixture. Stir in broth. Fill bird (do not pack), truss and roast as usual. Or spoon into greased 4-qt. casserole. Bake, covered, in moderate oven (350°) 35 minutes; uncover and bake 10 minutes more.