Place the turkey, egg, bread crumbs, ranch dressing mix, and 1 tablespoon of the Worcestershire sauce into a mixing bowl along with 3 tablespoons of the minced onion, and 3 tablespoons of the minced bell pepper. Set the remaining onion and bell pepper aside. Form the turkey mixture into 2 inch meatballs, and place into a 9x13 inch baking dish.
Bake uncovered in the preheated oven for 15 minutes. While the meatballs are baking, stir the remaining onion and bell pepper in a bowl along with the Dr. Pepper(R), 1 tablespoon Worcestershire sauce, ketchup, diced tomatoes, salt, black pepper, and garlic powder. Once the meatballs have cooked for 15 minutes, remove them from the oven and pour the sauce overtop. Cover the dish with aluminum foil and return to the oven.
Bake for 30 minutes, then remove the foil and continue baking 15 minutes more. Remove from the oven and allow to stand 15 minutes before serving.
