Lamb Leg Roast Cooking Time: The Complete Guide

Lamb leg roast is a delicious dish that many people enjoy. However, it’s easy to get lost in the confusion of lamb leg roast cooking time.

lamb leg roast cooking time
Lamb Leg Roast and Salad. Credit: canva

Cooking time varies depending on the size of your lamb and what type of cooking method you use (oven or barbecue). It can be tricky to know how long it needs to cook, so we have created this guide for you.

In this blog post, we will explore the best ways to cook lamb leg roast depending on what your preferences are. We will also discuss how long you should expect each method to take. So, you can confidently prepare your meal without needing to worry if it’s going to be done in time for dinner.

What Is a Lamb Leg Roast?

A leg of lamb roast is a cut of meat that comes from the upper portion of the back legs of an animal. It’s also known as a saddle or hindquarter and can be cooked in many different ways.

Why Do You Choose the Lamb Leg?

The lamb leg roast is a versatile piece of meat that can be cooked in the oven, on the barbecue, or even smoked. And it’s absolutely delicious.

If you want a simple, lean roast lamb cut, go for a leg of lamb. You can buy a whole leg that is bone-in leg, part bone-in, or boneless.

A whole leg makes a beautiful centerpiece and retains flavor from the bone. A boneless leg is easier to serve and carve too, or you can also choose a part-boned leg in the middle.

Butterflied lamb leg roast is a leg of lamb that has the leg bone removed and the meat opened out to form a butterfly shape. This cut is often used for barbecuing. But it can also be used to cook a roast because the meat is flat and it cooks quickly.

A whole leg of lamb is usually about 2-2.75kg and will serve 6-8 people. If you are cooking for a smaller group, get the half leg instead.

If you are cooking a boneless lamb roast, leg, or shoulder, it should be 225g per person. For 6 people, the meat should weigh between 1.5 – 2kg. Buy a larger piece of meat than you need, because when it cooks the meat will shrink.

How to Cook Lamb Leg Roast?

lamb leg roast
Roasted Lamb Leg. Credit: canva

Defrost your leg of lamb

Defrost your meat in the fridge or in a cool room below 10–15C rather than at room temperature, so that the outside remains cold. It is particularly important to ensure that poultry is fully defrosted before cooking.

Add seasoning

There are many ways you can add to and enhance the flavor of your roast lamb. Start with something simple like leg of lamb seasoned with rosemary and garlic.

There are many ways you can add to and enhance the flavor of your roast lamb. Start with something simple like rosemary and garlic

If you like your lamb plain and simple, just sprinkle it with salt before you cook it.

Get cooking

  • Preheat the oven or barbecue to the recommended oven temperature for your cut.
  • Put the meat on the roasting rack.
  • Follow the recommended roasting time for your cut’s weight.
  • Check the lamb roast internal temperature with a meat thermometer or instant-read thermometer.
  • Remove the cooked lamb roast before it reaches the final temperature as it continues to cook while resting.

Baste the lamb

Basting means to spoon the juices from the roasting tin back on the meat that is cooking. When you take the roasting tin out of the oven rack, tilt it so that all of the fat and juices collect in one corner. Baste the lamb 2 or 3 times while it is cooking. Remember to shut the oven door when you baste.

Rest the meat

Once you cook the meat, put it in a warm place covered with tented foil for the time that is listed in the calculator. This will make it juicier and easier to carve.

How to Determine Lamb Leg Roast Cooking Time?

roast lamb leg in oven
Raw Lamb in Oven. Credit: canva

Cooking time for the lamb roast is the amount of time it takes to cook a roast. It can vary depending on the lamb cuts, what type of cooking method you use, and how well done you want your meat to be.

Roast Lamb Cooking Time and Temperature Guidelines

  • Weight per 500g (approximate)
  • Internal temperature goal

Oven Roast Lamb Cooking Time and Oven Temp

Eye of loin/backstrap, lamb round, topside roasts, mini roast, lamb rump

  • Oven temp. (NO FAN): 220°C
  • Rare (58°C): 22 min per 500g
  • Medium (65°C): 28 min per 500g
  • Well done (70°C): 32 min per 500g

Rack of lamb, four-rib roast, crown roast

  • Oven temp. (NO FAN): 200°C
  • Rare (58°C): 24 min per 500g
  • Medium (65°C): 33 min per 500g
  • Well done (70°C): 43 min per 500g

Loin (boned and rolled) easy-carve leg or shoulder

  • Oven temp. (NO FAN): 180°C
  • Rare (58°C): 19 min per 500g
  • Medium (65°C): 26 min per 500g
  • Well done (70°C): 30 min per 500g

Butterflied lamb leg

  • Oven temp. (NO FAN): 180°C
  • Rare (58°C): 12 min per 500g
  • Medium (65°C): 15 min per 500g
  • Well done (70°C): 18 min per 500g

Butterflied lamb shoulder

  • Oven temp. (NO FAN): 180°C
  • Rare (58°C): 22 min per 500g
  • Medium (65°C): 25 min per 500g
  • Well done (70°C): 29 min per 500g

Boneless lamb shoulder (Boned and rolled)

  • Oven temp. (NO FAN): 180°C
  • Rare (58°C): 19 min per 500g
  • Medium (65°C): 26 min per 500g
  • Well done (70°C): 31 min per 500g

Barbecue Roast Lamb Cooking Time and Temp

Lamb round, topside roasts, lamb rump

  • Barbecue temp.: 200°C
  • Rare (60°C): 20 min per 500g
  • Medium (65-70°C): 25 min per 500g
  • Well done (75°C): 30 min per 500g

Rack of lamb

  • Barbecue temp.: 200°C
  • Rare (60°C): 20-25 min total (regardless of weight)
  • Medium (65-70°C): 30-35 min total (regardless of weight)
  • 4Well done (75°C): 40-45 min total (regardless of weight)

Leg or shoulder (bone-in), easy-carve leg, shoulder

  • Barbecue temp.: 180°C
  • Rare (60°C): 25 min per 500g
  • Medium (65-70°C): 30 min per 500g
  • Well done (75°C): 35 min per 500g

Slow Cooking Time

As a general rule, if using a slow cooker, we recommend simmering or slow-roasting lamb at 160–180°C for two hours.

Leg of Lamb Cooking Time Calculator

The great thing is that BBC UK provides a roast calculator to calculate the cooking time for various meats and different parts of meats, including leg of lamb.

It is very easy and simple to use.

You can check here: Roast Calculator

Simple Guides to Different Size of Leg of Lamb Cooking Time

roasted lamb leg
Sliced Lamb Roast. Credit: canva

This simple guide is calculated the approximate cooking times, by using the above roast calculator (medium).

  • 2.5kg leg of lamb cooking time:
  • First brown: 20 mins (at 220°C), then cook: 1 hrs 40 mins (at 180°C), then rest: 30 mins (in a warm place)
  • 1.8kg leg of lamb cooking time:
  • First brown: 20 mins (at 220°C), then cook: 1 hrs 12 mins (at 180°C), then rest: 30 mins (in a warm place)
  • 1.4kg leg of lamb cooking time:
  • First brown: 20 mins (at 220°C), then cook: 56 mins (at 180°C), then rest: 30 mins (in a warm place)
  • 1kg leg of lamb cooking time:
  • First brown: 20 mins (at 220°C), then cook: 40 mins (at 180°C), then rest: 30 mins (in a warm place)
  • Half leg of lamb cooking time: depending on the size and weight of the half leg.

How Do You Know When the Lamb Leg Roast is Done Cooking?

When the cook time is up, use a skewer to check on your lamb’s degree of doneness. Stick it into the thickest part of the lamb meat. If it slides in easily, then your cooked lamb leg is done.

If the lamb juices are pink, then it is medium-rare. If the juice is slightly pink, it will be medium. When you want to eat well done, they should run clear. Use a meat thermometer to make sure.

The lamb will be cooked through and slightly falling apart, so you can’t use the words medium, medium-rare, or well done.

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