Directions Preheat an outdoor grill for high heat. Coat one side of a large piece of aluminum foil with cooking spray. Place beets and butter on foil; season with salt and pepper. Wrap foil over beets. Place packet on the grill grate. Cook 30 minutes, or until beets are very tender. Allow beets to cool about 5 minutes before serving. You don't even need to peel to enjoy!