In a 9- by 13-inch baking dish, mix wine, soy sauce, oil, garlic, chopped cilantro, and bay leaves. Spread lamb open in the marinade and turn to coat. Cover and chill, turning meat occasionally, at least 4 hours or up to 1 day.
Lift lamb from marinade (reserve marinade) and lay flat (open) on a barbecue grill over a solid bed of medium coals or medium heat on a gas grill (you can hold your hand at grill level only 4 to 5 seconds). Close lid on gas grill. Cook, turning as needed to brown meat evenly, until a thermometer inserted in thickest part is 135° to 140° for rare, 30 to 45 minutes; thin portions will be well-done. Brush meat occasionally with marinade up until the last 10 minutes of cooking.
Transfer meat to a platter, keep warm, and let rest 5 to 15 minutes. Garnish with cilantro sprigs. Thinly slice meat. Add salt and pepper to taste.