DO-AHEAD TIP: Marinate lamb overnight or for at least 5 hours (see recipe).
Place lamb in a large zipper-topped plastic bag.
In a food processor, combine remaining ingredients (olive oil through thyme); blend until smooth. Pour mixture over lamb; seal the bag and refrigerate overnight or for at least 5 hours.
At time of cooking, preheat oven to 400 degrees. Place leg of lamb in a roasting pan or large baking dish; pour marinade over the top and bake for 40 to 50 minutes or until desired level of doneness is achieved.