Whisk together the red wine, olive oil, mustard, garlic, rosemary, thyme and black pepper in a large resealable container or a glass dish. Add the butterflied lamb, turning to evenly coat. Refrigerate at least 2 hours or for up to 24 hours.
Before cooking, remove the dish with the lamb from the refrigerator and let stand at room temperature for 30 minutes.
Prepare outdoor grill with hot coals, or heat gas grill to hot, or heat broiler. Season the lamb on both sides with the salt.
Grill the lamb, uncovered, or broil the lamb 6 inches from the source of heat for 10 minutes. Flip the lamb over. Cover the grill and continue to grill, or continue to broil, until the internal temperature registers 140°F on an instant-read thermometer inserted into the center of the meat, another 8 to 10 minutes. Remove the lamb to a platter; let rest for 10 minutes before slicing.
Ask your butcher to butterfly the leg of lamb for you. You may have to pound the thicker parts of the lamb slightly so the meat is a uniform thickness to ensure even cooking. To butterfly the lamb yourself, place the boneless leg on a cutting surface. With a chefs knife and holding the blade parallel to cutting surface, slice through center of lamb without cutting all the way through. Spread open the lamb like a book. Flatten any uneven or thicker parts of the meat.