"Roasts bring people together, turning a meal into a shared experience. The slow-cooked flavours and the tradition of carving make each occasion feel like a genuine celebration. For my family roasts, I usually turn to a perfectly roasted leg of lamb. I season the lamb with garlic and rosemary, then slow-cook it until it’s beautifully tender and flavoursome - simple, but truly delicious. It’s the kind of roast that makes any gathering feel special. My number-one rule for roasting meats is to let the meat come to room temperature before cooking; it ensures even cooking and a perfect roast. And don’t forget to rest it after it comes out of the oven – this lets the juices settle and keeps everything juicy and tender." – Matt Moran

What you need to know before you start

This recipe takes roughly 2 hours to prepare. Before you begin, take your lamb leg out of the fridge and let it come to room temperature to ensure even cooking. It roasts in the oven for 1 hour 40 minutes, however don’t stray too far from the kitchen, as the lamb needs to be basted every 30 minutes with the pan juices.

To prepare the dish, you’ll need basic equipment including a roasting dish, a sharp knife, a pastry brush and access to an oven and food processor. To carve, use a large, sharp knife and a steady hand. 

Why is this the best rosemary and mustard roast lamb leg with mint sauce recipe?

This homemade whole lamb leg roast recipe by Australian chef and restaurateur Matt Moran is the perfect family meal. It incorporates classic flavours like earthy rosemary, sweet and spicy mustard and juicy lamb with a bright and tangy mint sauce that comes together in an impressive yet achievable dish. Brushing the lamb with the mustard combination, drizzling with oil and seasoning with salt flakes and freshly ground black pepper all help the lamb to develop an amazingly delicious crust as it roasts. 

Your friends and family will look on in awe as this whole lamb leg hits the dinner table accompanied by the bright mint sauce, roast potatoes and steamed greens – ideal for your Sunday night dinner or Christmas feast. 

How long should a leg of lamb take to cook?

For this recipe, a 2.5kg lamb leg with bone in takes 1 hour 40 minutes to cook in the oven, with 20 minutes of resting time. The lamb should be cooked through, tender, yet still blushing-pink on the inside. 

Which cooking method is best for a leg of lamb?

There are a number of different ways you can cook a leg of lamb. The perfect one for you will depend on taste preference, what cooking equipment you have available and any time restraints. The main methods of cooking include oven-roasting (like this recipe) or slow-roasting at a lower temperature for 4-5 hours. This can be done in the oven or in a slow-cooker. When in doubt, always go for roasting meat on the bone, as the meat will be more tasty and tender.

What ingredients you’ll need

Lamb leg: We use a 2.5kg lamb leg with the bone in for juicy and flavourful results.

Garlic cloves: Garlic pieces spike the lamb leg, infusing the meat with a rich, savoury aroma and mellow flavour when roasted.

Rosemary: Similarly, fresh rosemary is inserted into incisions made over the lamb to add fragrant, woodsy notes. 

Dijon mustard: Dijon mustard contributes a sharp, tangy flavour that helps to balance the richness of the lamb. 

Wholegrain mustard: Wholegrain mustard adds a textural contrast with subtle pops of spice and tanginess.

Extra virgin olive oil: Olive oil generously coats the whole lamb leg to impart a slightly rich, fruity base that helps to moisten the lamb, and ensures a crispy crust when roasted. 

Mint: The main ingredient for the mint sauce. It provides a fresh, aromatic flavour to create a cool, slightly sweet contrast to the rich, savoury lamb.

Grapeseed oil: This mild and neutral oil helps to carry the flavour of mint while helping to create a smooth and velvety sauce. 

Malt vinegar: Vinegar introduces a tangy, slightly malty acidity that balances the sweetness of the mint and sugar, brightening the sauce and cutting through the richness of the lamb.

Brown sugar: Brown sugar adds a subtle sweetness and molasses-like depth that helps to round out the flavours of the sauce.

Roasted potatoes and steamed greens: Complete the dish with classic side dishes like roasted spuds and fresh steamed greens. 

Should leg of lamb be cooked covered or uncovered?

To prepare this recipe, begin by brushing mustards over a room temperature lamb leg. Season and roast in a 200°C/180°C fan-forced oven for 1 hour 40 minutes uncovered. There’s no need to cover the lamb until it comes out of the oven and is resting. Cover it with a loose piece of foil for 20 minutes before carving and serving. If slow-roasting lamb, cover for the first few hours to prevent the meat from drying out, then roast uncovered to finish and brown and caramelise the meat.

How to store leftover roast lamb leg

To store any leftover lamb, let it cool before slicing and portioning into plastic zip-lock bags or airtight containers. Place in the fridge and consume within 2 days. You can also freeze the lamb – wrap it in several layers of plastic wrap and foil to prevent freezer burn. 

What to serve with rosemary and mustard roast lamb leg with mint sauce

While this rosemary and mustard roast lamb leg is a feast on its own, we recommend serving it with your favourite sides to complete the dish. Think golden roast potatoes, steamed broccolini, eggplant wedges or a hearty roast pumpkin, feta and grain salad. 

Don’t forget generous servings of that homemade mint sauce, a gravy or even a simple dollop of yoghurt. 

Drink pairings with rosemary and mustard roast lamb leg

delicious. Drinks Editor Mike Bennie recommends pairing your roast lamb with a light red wine or zesty white. This includes a light-bodied vermentino, a dry and acidic Italian sangiovese or a bolder shiraz. 

If you love our rosemary and mustard roast lamb leg with mint sauce recipe, try this 

Looking for the perfect main course for Sunday roast or your festive feast? Look to these fan-favourites that are sure to impress:

• Aphrodite’s roast chicken
• Colin Fassnidge’s slow-roasted lamb shoulder
• Herb and garlic porchetta