1/4 cup shredded part-skim mozzarella or Monterey Jack cheese, divided
Cut each zucchini in half lengthwise. Scoop out pulp, leaving a 1/4-in. shell; set aside. Chop zucchini pulp; set aside.
Crumble sausage into a small skillet; add onion and celery. Cook over medium heat until sausage is no longer pink; drain. Stir in the croutons, 2 tablespoons cheese and zucchini pulp. Spoon into zucchini shells.
Place in an ungreased baking dish; add 1/4 in. of water. Cover and bake at 350° for 20 minutes. Uncover; sprinkle with remaining cheese. Bake 5 minutes longer or until zucchini is tender.