Roast Leg of Lamb (Garlic Herb Oil Marinade) Bone-In

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Roasting a leg of lamb is simple and easy. This recipe uses bone-in lamb with a garlic herb and olive oil marinade. Packed with flavor this is a recipe to impress. Serve it with mashed or roasted potatoes, salad, and bread for a wonderful festive meal. Leftovers are great in sandwiches and wraps.

Lamb leg on a serving platter. — How to Roast Lamb Leg

A leg of lamb is a very impressive cut of meat. It comes from the back haunches of the animal. You can buy it boneless or bone-in. The average weight of a lamb leg is around 5 to 7 lbs. It is best to buy a medium not too young and not too old lamb otherwise the meat can be quite tough.

Why make this leg of lamb

This is my super easy lamb to make any time of the year. Plus, it is so packed with flavor.
Today, I am using garlic, herbs, and oil marinade without any butter and yet, look at the wonderful color I got on this meat.
Having said that, no matter what marinade you use, you can use the same process to roast lamb successfully every single time.
Most of the ingredients used are simple pantry staples plus fresh herbs.
You can marinate the meat for as little as 15 to an hour, or up to 12 hours in the fridge.
Today, I am using bone-in lamb leg but you can also use boneless leg of lamb or lamb shoulder with this marinade.
You can use leftover lamb for sandwiches and wraps or in my chicken pot pie or shepherd's pie.

A sliced lamb leg on a wooden board. — How to Roast Lamb Leg

Timeline for making this lamb

Knowing how long you will need for your dish is important when planning a meal. Take into account that you can use the oven simultaneously.

Make the garlic herb marinade - 10 mins
Marinate the lamb - 15 mins up to 12 hours.
Roast the lamb - 60 to 90 mins
Rest the lamb - 15 mins
Make gravy - 10 mins (optional)

A plate of mashed potato toped wit lamb. — How to Roast Lamb Leg

Ingredients and substitutes

Lamb - I am using the bone-in leg of lamb. But, you can also use the shoulder for this recipe. Just make sure to thaw the meat an hour or two before roasting. Read more about cuts of lamb.
Herbs - For red meat, it is very important to use fresh herbs. And yet, you can also use 1 teaspoon dry rosemary and 1 teaspoon dry thyme in the marinade.
Lemon juice - helps tenderize the meat as well as rounds all the flavors together. I highly recommend not to substitute it.
Spices - Smoked paprika and mild coriander add a subtle delicate flavor. You can also use ½ teaspoon cumin to add some extra smoky flavor as well.
Garlic - This has to be fresh garlic. As you can see, we do have a nice generous portion of garlic for flavor.

Ingredients for roasting leg of lamb. — Ingredients How to Roast Lamb Leg

Leg of lamb with garlic oil marinade

Prep Lamb - Trim excess fat off the lamb and pat dry on all sides.
Pro tip - if the lamb is wet the marinade will slide off the meat as soon as it starts cooking. If the meat was frozen ensure that it is thawed at least an hour before marinating.
Marinade - In a mortar and pestle (or use a food processor) - crush the garlic, rosemary, and thyme. Add the paprika, coriander powder, olive oil, and lemon juice. Set aside.

Progress pictures a mortar and pestle with garlic herb marinade. — Progress Pictuers How to Roast Lamb Leg

Marinate the lamb - Season the lamb with salt and pepper on all sides. Then, brush the marinade on all sides. Leave to marinate for an hour or up to 12 hours in the fridge. Thaw at least an hour or two before roasting.
Pro tip - this is a large chunk of meat and not much exposed so make sure to generously season with salt and pepper. Some of it will be absorbed inside the meat.
Preheat the oven at 350°F / 180°C / Gas mark 4

Progress pictures a roasting the lamb leg. — How to Roast Lamb Leg

Place the leg of lamb in a roasting pan on the roasting rack. If using a thermometer add it in the center in the thickest part of the meat.
Roast until you reach the desired temperature of doneness.-
- Medium rare - between 130 F to 135 F, approximately 20 minutes per pound.
- Medium - between 135 F to 140 F, approximately 22 to 23 mins per pound
- and Medium well - between 145 F to 150 F, approximately 25 minutes per pound
- Well Done is between 155 to 165 F, approximately 30 minutes per pound.
When the thermometer reaches your desired temperature, remove the lamb from the oven. Loosely tent it with aluminum foil and let rest for at least 15 minutes before slicing. In the meantime make the gravy.
Serve with mashed potatoes or roast potatoes

A roasted leg of lamb on a wooden board. — Easy How to Roast Lamb Leg

There are three secrets to cooking red meat

Good meat - buy good quality meat from the right source. That way, you will have meat that's right for what you're cooking.
A good marinade - this does not have to be a long list of ingredients. In fact, salt, pepper, and lemon juice are usually enough. However, add some fresh herbs and spices to take it to the next level.
Cook it just right - don't undercook or overcook it. And, the best way to get it right, stress-free, is to use a thermometer so there is no calculation and no guessing. When the thermometer reaches the desired internal temperature, your meat is ready.

A platter with roasted leg of lamb. — How to Roast Lamb Leg

Sides to serve with lamb

Tips for Success

You want to choose a well-marbled piece of meat with a decent amount of fat on top. The fattier the meat the more juicy and flavorful the roast.
Always thaw the lamb before cooking - a few hours at least 2 to 3 hours. Cooking chilled meat can result in uneven baking causing the outer parts of the meat to overcook.
A leg is a large chunk of meat and not much exposed. So, make sure to overseason the meat, because only some of it will penetrate the meat. The rest of it will get crusted on.
Use a roasting rack, don't just place the meat on the baking tray. The roasting rack will let the juices flow below and let the outside of the leg forms a crust almost a sear that keeps all the juices in.
Elevate the bone from the base if possible. This encourages even cooking by circulating the air.
Cook the meat just until you reach the desired doneness, not a minute more. The meat continues to cook to about 5 to 10 degrees more after you take it out of the oven.
If you are entertaining and want to ensure you have the perfect roast. Remove the lamb at about 135 F - this will be perfectly pink and about 140 F by the time you serve.
Don't open the oven door too often to check doneness. Instead, calculate the cooking time and check closer to the time.
Don't poke too many holes in the meat while checking for doneness. The moment you poke a hole in the meat you will see juices flow out. You want these to stay in so don't make too many holes. I poke the thermometer just once and leave it there until it reaches the desired temperature.
Let the meat rest after cooking. If you cut the meat too soon all the juices will flow out of the meat and give you a dry roast. Instead, let the meat rest for at least 15 minutes if not more.

More lamb recipes

How long will this leg of lamb keep?

If stored properly, a roast leg of lamb will keep in the fridge for 3 to 4 days. You can also freeze it for up to a month.

Do I need a meat thermometer for this roast?

I personally prefer to use a meat thermometer so I don't have to calculate and watch the clock ever so often. But, you can certainly do without it. However, if you are new to cooking or roasting meat, a thermometer can take the guesswork out. The most important point to note is to make sure you insert the thermometer needle in the middle deepest part of the thick meat.

How long do you cook a leg of lamb for?

I cook my lamb medium-rare, about 135 F, using a meat thermometer. But, if you don't own a thermometer here's a guide you can use.
- Medium rare - between 130 F to 135 F, approximately 20 minutes per pound.
- or Medium - between 135 F to 140 F, approximately 22 to 23 minutes per pound.
- and Medium well - between 145 F to 150 F, approximately 25 minutes per pound.
- Well Done is between 155 to 165 F, approximately 30 minutes per pound