Combine turkey, bread crumbs, spinach, egg, onion powder, and garlic powder together in a bowl. Roll mixture into palm-size meatballs and place 2 inches apart on a baking sheet.
Bake in the preheated oven until no longer pink in the center and outside is browned, 15 to 20 minutes. An instant-read thermometer inserted into the center should read at least 165 degrees F (74 degrees C).
