Place bread slices in single layers on 2 baking sheets. Bake at 325° for 25 minutes or until almost crisp, using both racks in oven. Tear bread into small pieces, and place in a 4-quart bowl.
Bring 8 cups water to a boil in a Dutch oven; add cabbage, and cook, uncovered, 3 minutes. Drain and immediately run cold water over cabbage; pat dry with paper towels. Add to bread in bowl, and set aside.
Cook apple, onion, celery, and garlic in 1/4 cup butter in a large skillet over medium heat 10 minutes or until tender, stirring often. Add apple mixture to cabbage; stir in salt and pepper.
Pour cider and broth over bread mixture, tossing gently. Spoon mixture into a buttered 13" x 9" baking dish; drizzle with remaining 1/4 cup melted butter. Bake, uncovered, at 350° for 40 minutes or until lightly browned.