Rub the Chateaubriand on both sides with salt and pepper. Place meat in shallow pan; add bay leaf, onions, and garlic. Drizzle with oil. Cover and marinate in refrigerator 2 to 3 hours, turning meat once or twice. Drain meat and discard marinade. Grill over medium-hot charcoal, turning to brown evenly. Continue cooking over indirect heat in covered grill, about 25 minutes, turning frequently, until meat is desired degree of doneness.