Step 1

Preheat the oven to 300°F.

Step 2

Cut the onion and orange into quarters. Break up the head of garlic and remove the skin, or peel and prepare 15-20 cloves. Rough chop the celery and set it all in the bottom of a large roasting pan with the carrots and rosemary.

Step 3

Season both sides of the leg of lamb generously with kosher salt and black pepper. Place the bone-side up and pour the beef broth and water over it.

Step 4

Pour the olive oil over the lamb, cover with aluminum foil, and roast in the hot oven for 5 hours (See Note 2 for different weights and roasting times).

Step 5

Remove from oven and set aluminum foil aside. Flip the leg of lamb carefully, bat with pan juices, and roast, uncovered, for 45 minutes or until the outside is a rich, golden brown.

Step 6

Keep lamb warm on a serving plate covered with aluminum foil after removing it from the pan.