Bone-in lamb loin is a large cut of meat that is more tender when cooked than traditional lamb loin. Traditional lamb loin is rolled with the bone removed, which can cause the meat to dry out faster. While there are other ways to prepare bone-in lamb loin including smoking and curing, the only practical method for most home chefs because of the size is to bake the meat in the oven. The bone-in lamb loin will require you to cook the lamb loin a little longer than traditional boneless lamb loin, but the extra flavor and succulent meat is worth an extra few minutes per pound.
Remove the bone-in lamb loin from the refrigerator and wrap it with plastic wrap. Set it on counter to allow it to warm up to room temperature, which should take about an hour.
Preheat the oven to 425 degrees Fahrenheit.
Remove the plastic wrap and brush the outside of the bone-in lamb loin with the melted unsalted butter and extra virgin olive oil on a cutting board or clean work surface. Rub the outside of the bone-in lamb loin with sea salt or kosher salt and freshly ground black pepper to taste.
Place the bone-in lamb loin in a roasting rack in a large roasting pan. Tighten the sides of the roasting rack to gently squeeze the lamb loin.
Put the lamb loin in the oven on the center rack for 90 minutes. Do not open the oven door as it is cooking.
Check the internal temperature of the bone-in lamb loin with an instant-read thermometer at the thickest point without touching the bone. The lamb loin should be a minimum of 120 degrees F inside for rare meat, 130 to 135 degrees F for medium rare and 140 to 145 degrees F for medium.
Things You'll Need
2 lb. bone-in lamb loin
2 tsp. melted unsalted butter
1 tbsp. extra virgin olive oil
Cutting board or clean work surface
Sea salt or kosher salt, to taste
Freshly ground black pepper, to taste
Roasting pan with roasting rack
Freshly chopped or dried rosemary, optional, to taste
You can rub the bone-in lamb loin with freshly chopped or dried rosemary to taste for a bit of extra flavor when you apply the sea salt or kosher salt and freshly ground pepper.
Avoid cooking bone-in lamb loin past medium-rare, as the meat will start to dry out and lose flavor.