Preheat oven to 400°F. Lightly grease a 9 x 13-inch casserole pan if desired.
In a mixing bowl combine 2 1/2 cups herb seasoned bread crumbs, 1/2 cup chicken broth (fat-free) or water, and the 15 ounces petit diced tomatoes with their liquid. Stir until the crumbs are moistened; set aside.
Place 1 1/2 pounds boneless, skinless chicken breasts (cut into small bite-sized pieces) in the prepared 9 x 13-inch pan.
Sprinkle 1/2 teaspoon garlic powder, 1/2 teaspoon black pepper, 1/2 teaspoon salt, and 1 1/2 teaspoons dried oregano evenly over the chicken. Add 3/4 cup mozzarella (part-skim).
Toss the chicken, seasonings, and 3/4 cup mozzarella in the pan until the pieces are evenly coated.
Spread the bread crumb and tomato mixture evenly over the chicken.
Sprinkle the remaining mozzarella (the remaining 1/4 cup) evenly over the breadcrumb layer.
Bake uncovered at 400°F for 35 minutes, or until the chicken is cooked through (165°F internal temperature) and juices run clear.
Let the casserole rest 3–5 minutes before serving.