This boneless leg of lamb roast is marinated in a mixture of lemon zest, garlic and rosemary, then slow roasted in the oven for juicy, tender medium rare slices. You can use a variety of herbs for the gluten-free marinade (thyme, oregano and mint also work) and serve the lamb roast alongside crispy potatoes cooked in the remaining fat!
Now that I’m no longer catering parties every weekend, I don’t have as many opportunities as I used to to make a big roast. So when there’s an upcoming holiday, or more rarely, a chance to throw a big dinner party, I look forward to pulling out the stops with a pork loin roast, or in this case, an epic slow roasted boneless leg of lamb.
The Best Marinade for Roasted Lamb
Back in my twenties (also during the peak of my catering career), I hosting a big New Year’s Eve gathering where I served this bone-in roasted leg of lamb. The marinade was one of the best things I’ve ever created—a combination of preserved lemons and dried herbs.
Since jarred preserved lemons are a bit of a niche ingredient and bone-in leg of lamb a little more cumbersome than boneless, I decided to streamline this recipe by using a boneless cut of meat and whole lemon zest in the herb crust.
How to Roast a Boneless Leg of Lamb in the Oven
The beauty of using lemon zest in addition to the juice is that you get a subtle floral note that offsets the woody rosemary. The only thing to be careful of is making sure not to remove any of the white pith when you zest or peel your lemon. I prefer to use a peeler to get large pieces since you’re going to throw the zest, along with the herbs, into a small food processor anyway.
For the herbs, if you don’t like rosemary, any woody herb will work. Oregano and thyme are easy substitutions on that front. If going with a leafy green herb, mint would be a classic combination with lamb.
I recommend marinating your boneless leg of lamb overnight for the most potent flavor, but even just an hour in the marinade will produce tender, delicious roasted lamb.
What Type of Lamb to Buy
Most butchers can prepare a boneless leg of lamb for you. Often times, they will then tie the roast together with kitchen twine.
If they don’t manage to do this for you, don’t stress! This actually allows for you to get the marinade in every nook and cranny before rolling up the meat and tying it yourself. Simply marinate the boneless leg of lamb, then cut kitchen twine into 4 to 5 equal pieces.
Roll up the lamb width-wise (so it’s thicker rather than longer). Place the twine beneath the lamb roast an inch or two apart and tie each piece tightly.
If your lamb comes pre-rolled and tied, there’s no need to remove the twine. Just use your fingers to ensure that the marinade gets into the center of the meat.
All that said, you can easily do this lamb roast with a bone-in piece of meat. You’ll just want to aim for 15 more minutes of cook time for medium rare. Or simply go by the internal temperature called for in the recipe instructions.
What to Serve with your Boneless Leg of Lamb
The lamb will leave behind some great fat. My favorite thing to do is add halved baby potatoes directly to the pan and toss to coat in the oil and remaining marinade. Roast them in a 425 F degree oven for 20 to 30 minutes while the roasted lamb is resting.
Alternatively, you can go with a classic side like these gluten-free scalloped potatoes or this broccoli with caper pesto.
This boneless leg of lamb is so flavorful you don’t really need to serve a sauce on the side, though I love a simple full fat Greek yogurt with some herbs mixed in. If you’re not using the fat for potatoes, just pour that and any remaining juices from the roasting pan on top of the sliced lamb.
Read on for the full recipe for this slow roasted lamb!
With health and hedonism,
Phoebe
Lemon-Herb Slow Roasted Boneless Leg of Lamb
Servings 8
Ingredients
Instructions
Place the lamb on a clean work surface. Remove any thick pieces of excess fat, and score the remaining, especially the elastic looking sinew. (Translation: cut thin slits in the fat, about ¼ inch apart. This will help it melt away in the cooking process and allow the marinade to flavor the meat). If your boneless leg of lamb is already tied up from the butcher, just make sure you’re not cutting into the twine.
Zest both lemons either using a microplane or peeler. In either case, make sure not to remove the white pith with the yellow rind (it can be bitter).
Place all the lemon zest, along with the garlic, rosemary, 1 tablespoon sea salt, and olive oil in the bowl of a small food processor. Add the juice of 1 lemon (approx. ¼ cup) and pulse until the herbs and zest are finely chopped. Alternatively, you can use a mortar and pestle to create a coarse paste.
Transfer the lamb to large mixing bowl and pour the marinade over the meat, using your hands to get it into every nook and cranny. If your leg of lamb is already tied, use your fingers to get some of the herb and lemon mixture into the center cavity.
Marinate the boneless leg of lamb for at least one hour at room temperature, or overnight covered in the fridge.
When you’re ready to cook, preheat the oven to 425 degrees F.
If your lamb is not already tied together, roll it up width-wise (i.e. the narrower part rolls into itself, so you’re left with one thick roll) and fasten it with 4 to 5 pieces of kitchen twine spaced 2 inches apart.
Place the marinated boneless leg of lamb on a baking sheet or in a roasting pan (I line mine with parchment for easier clean up) with the fattier side facing up. Cook for 15 minutes, then turn the heat down to 350 F and roast for another 45 to 60 minutes (depending on the thickness), until the internal temperature is 130 – 135 degrees for medium rare. The rule of thumb is 15 minutes of cook time per pound of lamb, so if your lamb roast is on the smaller side (3lb), you’ll aim for 45 minutes.
Remove the lamb roast from the oven, transfer to a carving board, and let it rest for at least 30 minutes. Cut away the twine and discard. Thinly slice the lamb against the grain (sometimes it’s easier to unroll the meat so you get smaller pieces.)
Pour any remaining juices from the pan over the lamb roast and serve warm or at room temperature alongside some crispy potatoes (see note).
If you make this, tag @phoebelapine and #feedmephoebe – I’d love to see it!