Cooking a leg of lamb on a gas BBQ can seem daunting, but with some simple preparation and techniques, you can achieve tender, juicy, and flavorful results. A gas grill provides an excellent way to get that classic smoky and charred exterior while keeping the inside pink and moist. With a few tips on choosing the right cut, preparing the lamb, managing the heat, and monitoring doneness, your grilled leg of lamb will become a go-to entree for backyard barbecues.
Selecting and Preparing the Leg of Lamb
Choose the Right Cut
When selecting a leg of lamb for grilling, look for a bone-in or semi-boneless leg. The bone helps insulate the meat while cooking. Opt for a cut that is well-marbled with white fat flecks throughout as this keeps it tender and flavorful. The leg should weigh 6 to 8 pounds to get the best ratio of crispy outside to tender and juicy interior when cooked over a gas grill.
Trim Excess Fat
Examine the lamb leg and use a sharp knife to trim away any thick sections of visible surface fat. Remove the large pockets of external fat to prevent flare-ups during grilling. Leave just a thin layer over the top to help keep the meat moist.
Season Well
For the best flavor, season the lamb at least 24 hours before grilling. Use a dry rub of fresh rosemary, thyme, garlic, salt, and pepper. You can also stud the lamb with whole garlic cloves or make small slits to insert slivers of garlic. Massage the seasonings all over the leg so they penetrate deep into the meat. Then tightly wrap it in plastic and refrigerate overnight.
Bring to Room Temperature
Take the lamb out of the refrigerator at least one hour before cooking. This helps it cook more evenly, preventing a burnt outside and raw middle. Pat it dry with paper towels right before grilling.
Setting Up the Gas Grill for Indirect Cooking
Grilling a leg of lamb requires a slow, indirect cooking method next to the heat rather than directly over it. Follow these tips for best results:
Heat Only One Side
With a two or three burner gas grill, turn on just one of the burners to medium heat. For a larger grill, light burners on one half to create a hot zone for searing and a cooler zone for indirect cooking.
Use a Drip Pan
Place an aluminum drip pan on the unlit side under where you will put the lamb. Fill it halfway with water or broth to help add moisture and flavor.
Install a Probe Thermometer
Investing in a digital probe thermometer means you can insert the probe into the thickest part of the lamb and monitor the internal temperature without constantly opening the grill.
Keep the Lid Closed
Cooking indirectly with the lid closed helps circulate heat evenly around the lamb for thorough cooking. Only lift it to flip, baste, or check doneness.
Control Flare-Ups
Flare-ups from lamb fat can lead to burning, so trim excess fat and have a spray bottle of water on hand. Mist the flames to keep them under control if needed.
Grilling Times and Temperatures
The grilling time will vary greatly based on the size and thickness of your lamb leg as well as your desired doneness:
- For medium-rare lamb, cook to an internal temperature of 135°F which takes 18-25 minutes per pound.
- For medium lamb aim for 140-145°F and 25-30 minutes per lb.
- Well-done is over 150°F internal temp and will take 30+ minutes per pound.
Use a probe thermometer to carefully monitor the inner temp of the thickest section. Time alone won’t give an accurate reading of doneness. Let the lamb rest at least 15 minutes before slicing into it. The internal temperature will rise 5-10 degrees during resting.
Step-by-Step Grilling Instructions
Follow these simple steps for perfect grilled leg of lamb:
1. Prepare the Gas Grill
Trim and season the lamb leg at least a day ahead. On grilling day, prep the gas grill by igniting only one side to heat an indirect cooking zone. Place a drip pan with liquid on the unlit side.
2. Sear the Lamb
Once the grill reaches medium heat around 350°F, carefully place the lamb over the hot side. Sear for 2-3 minutes per side until nicely browned.
3. Indirect Cook
Move the seared lamb to the indirect, unlit side of the grill. Insert a probe thermometer in the thickest section. Close the lid to circulate heat.
4. Baste and Monitor
Baste the lamb with an herb marinade every so often. Check the probe after 15 minutes. Close the lid quickly between checks.
5. Finish Resting
Once the lamb reaches your desired internal temperature, remove it from the grill to a cutting board. Loosely tent foil and let rest 15 minutes.
6. Carve and Serve
Carve the well-rested lamb into slices. The meat should be tender and juicy. Serve with favorite side dishes or sauces.
Tips for Maximizing Flavor
Utilize these easy methods to infuse your grilled leg of lamb with delicious flavor:
- Marinate – Soak the lamb in a marinade up to 24 hours before grilling. Use oil, garlic, rosemary, lemon, yogurt or wine based marinades.
- Rub – Coat the lamb all over with a spice and herb rub at least 6 hours prior to cooking.
- Baste – Regularly brush the lamb with an herb-infused oil or melted butter as it grills.
- Smoke – Add soaked wood chips to the grill for a smoky flavor. Apple, oak or maple work well with lamb.
- Char – Allow the lamb to get nice char marks during the searing stage for caramelized flavor.
- Crust – Coat the leg with crushed peppercorns, mustard seeds, breadcrumbs or chopped herbs before grilling.
Experiment with different marinades, rubs and basting sauces to find your perfect combination of herb and spice flavors.
Common Mistakes to Avoid
It’s easy to commit a few errors that will leave your grilled leg of lamb dry or burnt. Here are some key mistakes to avoid:
- Skipping the sear – Always sear the lamb first to help lock in juices before indirect cooking.
- Cooking over direct heat – With a large cut like a leg, indirect even heat is essential.
- Turning too often – Only flip once or twice to get grill marks without drying out the meat.
- Incinerating flare-ups – Trim fat ahead and mist flames quickly to avoid burning.
- Cutting without resting – Letting the lamb rest ensures tender and juicy meat.
- Overcooking – Use a meat thermometer to avoid overcooking past your desired doneness.
- Forgetting to season – Proper seasoning and marinating is vital for flavorful lamb.
Frequently Asked Questions
What size leg of lamb is best for grilling?
Look for a bone-in leg of lamb that weighs between 6 to 8 pounds. This size will cook evenly over a gas grill. Much larger and it is harder to cook through without burning.
What is the most flavorful cut of lamb for grilling?
The leg is the most flavorful cut for grilling. It has great marbling and enough connective tissue to keep it moist over the grill, but not so much that it requires prolonged braising.
Should lamb be marinated before grilling?
Yes, marinating is highly recommended for flavor and tenderness. Lamb pairs well with rosemary, garlic, yogurt, wine, and citrus marinades. Let it marinate anywhere from 2 hours up to 24 hours.
What are the best woods for smoking lamb?
Apple, oak, maple and cherry impart a nice mild smoky flavor to lamb. Soak the wood chips before adding them to the hot coals or gas grill smoker box. Hickory and mesquite are too strong for lamb.
Is lamb done at 145°F?
An internal temperature of 140-145°F will give you lamb that is cooked to medium doneness. For a pinker medium rare, aim for 135°F. Let the lamb rest at least 15 minutes before slicing into it.
Can I grill a frozen leg of lamb?
Never throw frozen lamb directly on the grill. Always thaw it first in the refrigerator for 24-48 hours depending on the size. This ensures it cooks through properly without burning the outside.
Grilled Lamb Leg Recipe Ideas
Grilled leg of lamb pairs wonderfully with mint, garlic, rosemary and citrus flavors. Here are a few recipe ideas for marinades, rubs and sauces:
- Mint Pesto Marinade – Fresh mint, basil, garlic, lemon, olive oil and Parmesan makes a bright flavorful marinade.
- Moroccan Spice Rub – A blend of cumin, coriander, cinnamon, cayenne, paprika and brown sugar adds exotic aromas.
- Garlic and Herb Crust – Combine fresh chopped rosemary, thyme, oregano, garlic, salt and pepper and pat it onto the lamb leg.
- Lemon-Dijon Baste – Brush the lamb while grilling with a sauce of Dijon mustard, lemon juice, garlic and olive oil.
- Red Wine Reduction – Deglaze the drippings after cooking with red wine and rosemary for a rich sauce.
- Mint Chimichurri – Pulsed fresh mint, cilantro, garlic, olive oil and red pepper flakes make a bright topping.
Get creative with global spice blends and herb combinations to put a flavorful twist on basic grilled lamb. Invite friends over and impress them with your backyard cooking skills.
Conclusion
Grilling a leg of lamb over a gas BBQ may seem intimidating, but with the right cut, preparation, temperature control and cooking technique you can achieve delicious results. Always trim excess fat, season well in advance, sear over direct heat and then slow cook indirectly with the lid closed until it reaches your desired internal temperature. Monitor it closely and avoid flare-ups. Resting it afterwards ensures tender juicy meat. Employ various marinades, rubs and basting sauces to infuse it with flavor. Master these simple methods for grilling lamb and you will have the star dish at your next barbecue.