1. Combine the olive oil, wine, garlic, thyme, rosemary and salt in a small bowl and mix well. Place the lamb in a 13x9-inch dish and pour the mixture over the lamb, turning to coat. Cover and refrigerate for 2 hours.
2. Preheat the broiler or prepare a grill for medium-high heat.
3. Remove the lamb from the marinade (reserve the marinade). Grill or broil about 5 inches from the heat, occasionally turning the meat and brushing with the reserved marinade. Cook until an instant-read thermometer inserted in the center of a thick part of the meat registers 135F for medium rare, 20 to 30 minutes. Let the lamb rest for 5 to 10 minutes, then thinly slice against the grain.
Tip: About Butterflied Leg of Lamb
Be sure to buy a boneless, butterflied leg of lamb, which cooks much faster than a bone-in leg. A butterflied leg can be quite uneven in thickness, so some parts will cook more quickly than others, which is fine if you are serving both fans of medium-rare meat and meat that is more well-done. If all your guests prefer medium-rare, simply cut off the thinner parts of the leg as they are cooked to medium-rare.
Tip: All About Marinades