In a medium-size bowl, combine yogurt, lemon juice, lime juice, rosemary leaves, garlic, salt, and pepper. Place lamb into a deep baking pan; pour yogurt marinade over the lamb. Cover and refrigerate at least overnight or up to 3 days.
Remove lamb from refrigerator and allow to come to room temperature before proceeding. Scrape the marinade off the lamb, wipe the meat with paper towels, and season generously with salt and pepper.
Preheat Barbecue and brush the grill with oil to keep the lamb from sticking. Grill lamb approximately 10 to 15 minutes on each side for rare or until meat thermometer registers an internal temperature of 120 degrees F. to 130 degrees F. or desired temperature (see below).
Rare - 120 degrees F.
Medium Rare - 125 degrees F.
Medium - 130 degrees F.
This is the type of cooking and meat thermometer that I prefer and use in my cooking. I get many readers asking what cooking/meat thermometer that I prefer and use in my cooking and baking. I, personally, use the Thermapen Thermometer shown in the photo on the right. Originally designed for professional users, the Super-Fast Thermapen Thermometer is used by chefs all over the world. To learn more about this excellent thermometer and to also purchase one (if you desire), just click on the underlined: Thermapen Thermometer.
Remove lamb from grill and transfer onto a cutting board and cover with aluminum foil; let stand 15 minutes before carving. During this time the meat continues to cook (meat temperature will rise 5 to 10 degrees after it is removed from the oven).
To serve, transfer sliced lamb onto a serving platter. Garnish with fresh sprigs of rosemary.
Makes 8 to 10 servings.