Gather all ingredients. Preheat the oven to 350°F (175°C).

Cut deep slits on the top of the leg of lamb every 3 to 4 inches; push slices of garlic down into the slits. Generously season with salt and pepper.

Place lamb on a roasting pan; arrange several sprigs of fresh rosemary under and on top of the lamb.

Roast in the preheated oven for 1 hour and 45 minutes to 2 hours, or until an instant-read thermometer inserted into the center of the lamb reads at least 135°F (57°C) for medium-rare to medium doneness.

Cover lamb with aluminum foil and let rest for at least 10 minutes before carving.