Preheat oven to 400 degrees F (200 degrees C). Grease an 11x7-inch baking dish.
Combine bread crumbs, Parmesan cheese, salt, black pepper, and garlic powder in a shallow bowl. Beat egg and 1/4 cup ranch dressing in another shallow bowl; toss chicken in egg mixture until coated. Press chicken into bread crumb mixture and transfer to prepared baking dish.
Bake in preheated oven until chicken is no long pink in the center and juices run clear, 12 to 15 minutes. Serve with remaining 1/4 cup dressing as dipping sauce.
