Preheat oven to 400 degrees F (200 degrees C). Cover a baking sheet with aluminum foil; place a wire cooling rack on top and spray with cooking spray.
Put chicken into a gallon-size resealable plastic bag. Add ranch dressing; seal and shake bag to coat chicken evenly.
Mix panko, Parmesan cheese, garlic powder, and parsley together in a bowl; pour into bag with chicken. Seal and shake bag to coat thoroughly. Remove from bag; place on rack in a single layer.
Bake in the preheated oven until no longer pink in the center and the juices run clear, about 15 minutes. An instant-read thermometer inserted into the center should read at least 165 degrees F (74 degrees C). Turn broiler on high; broil until crispy, about 1 minute.