Preheat oven to 350 degrees F (175 degrees C).
Place chicken in a roasting pan, rub olive oil around all sides of the side then season generously inside and out with salt and pepper. Sprinkle inside and out with garlic and onion powder. Place the stick of butter in the chicken cavity.
Bake uncovered 1 hour and 15 minutes in the preheated oven, to a minimum internal temperature of 180 degrees F (82 degrees C). Remove from heat, and baste with melted margarine and drippings. Cover with aluminum foil, and allow to rest about 30 minutes before serving.