Heat the oven to 400°F and coat a 9-by-13-inch baking dish with cooking spray.
Stir the dry stuffing mix, broth and condensed soup together directly in the dish and spread it evenly.
Distribute the frozen broccoli over the stuffing, then arrange the chicken pieces across the top.
Season the chicken with garlic powder, salt and black pepper and cover the dish tightly with foil.
Bake for 35 minutes, then uncover and bake for 10 to 13 minutes more, until several center chicken pieces reach 165°F and the stuffing edges are crisp.
Rest for 5 minutes before scooping through all three layers.