In a large sealable plastic bag or a glass dish, combine all the ingredients.
Add the lamb and coat thoroughly. Cover and refrigerate for about 12 hours or overnight.
Preheat the grill, setting the burners on medium-low.
Drain the meat, keeping the marinade aside. Season the meat with salt and pepper. Insert a roasting pin through the leg of lamb and cover with aluminum foil. Install the pin in the grill spit. Cook for 1 hour and 30 minutes over medium-low heat.
Place a disposable aluminum baking pan under the leg of lamb. Fill with the marinade. Remove the aluminum foil and bake for about 1 hour, basting regularly with the marinade, until the meat has browned and is fork-tender. If necessary, add water to the marinade while cooking. Serve with the pan juices.
Recipes with the "Healthy Pick" stamp have been evaluated by a registered dietitian member of the Ordre professionnel des diététistes du Québec.