Preheat the oven to 425°F. Place chicken breasts into a Glad® gallon bag and pound until they are ¾ of an inch thick (optional). Place the chicken breasts in a baking dish to fit. Brush with the melted butter or olive oil on both sides. Sprinkle or shake the ranch seasoning mix over the chicken on both sides. If there is any remaining butter or oil, drizzle over the seasoned chicken.Place in the oven and bake for 18–20 minutes, until cooked through and no longer pink in the center. Remove from the oven and let rest for a few minutes. Serve hot.