Grilled Butterflied Leg of Lamb

7- to 8-pound leg of lamb, trimmed of all fat, boned, and butterflied by butcher (4 to 4 3/4 pounds boneless)
1 lemon

Ingredients for the herb rub:
8 garlic cloves
3 T chopped fresh thyme leaves
2 T chopped fresh rosemary leaves
2 T chopped fresh parsley leaves
1/2 teaspoon freshly ground black pepper
1 T coarse salt
3 T olive oil

Preparing the lamb:
Finely chop garlic and in a small bowl stir together with remaining herb-rub ingredients.

Put lamb in a large dish and with tip of a sharp small knife held at a 45-degree angle cut 1/2-inch-deep slits all over lamb, rubbing herb mixture into slits and all over lamb. Marinate lamb at room temperature 1 hour.

Prepare grill.

Lightly pat lamb dry. On a lightly oiled rack set 5 to 6 inches over glowing coals grill lamb about 10 minutes on each side, or until an instant-read thermometer horizontally inserted into thickest part of meat registers 125 degrees F for medium-rare.

Cut lemons in half and grill.

Alternatively, roast lamb in a roasting pan in middle of a 425 degrees F oven about 25 minutes, or until an instant-read thermometer horizontally inserted into meat registers 125 degrees F for medium-rare.

Transfer lamb to a cutting board. Squeeze roasted lemon juice over lamb and let stand, loosely covered with foil, 15 minutes.

Cut lamb into slices and serve with any juices that have accumulated on cutting board.