Cooking spray 3/4 cup shredded zucchini (about 1 small zucchini) 12 ounces ground turkey 1/3 cup shredded yellow onion (from 1 small onion) 1/2 teaspoon dried oregano 1/4 teaspoon kosher salt 1/4 teaspoon black pepper 1 large egg 1 tablespoon olive oil 8 ounces sliced cremini mushrooms 2 garlic cloves, minced 1 1/2 cups lower-sodium marinara sauce (such as Rao's or Dell'Amore) 1/4 cup water 4 ounces part-skim mozzarella cheese, shredded (about 1 cup) 4 ounces whole-wheat baguette, cut into 24 thin slices and toasted