How To Make Grilled Lamb Loin Roast Outdoors

Lamb loin roast makes for an elegantly delicious main course to serve at your next backyard gathering or take on a camping trip.

The tender, juicy meat soaks up smoky grill flavors and pairs perfectly with fresh veggies or side salads. Grilling the roast outdoors adds festive summertime flair to this impressive entrée.

Follow these simple steps for grilling lamb loin to tender, rosy perfection. Your guests will be begging for seconds!

Ingredients

• 1 whole boneless lamb loin roast (about 2 1⁄2 – 3 lbs)
• 3 tablespoons olive oil
• 3 cloves garlic, minced
• 2 tablespoons fresh rosemary, chopped
• Salt and pepper to taste
• Wooden skewers, soaked in water 30 mins

Equipment

• Gas or charcoal grill
• Meat thermometer
• Basting brush
• Aluminum foil

Step 1 – prepare the lamb

Rinse the lamb loin and pat it completely dry with paper towels. Place it on a large piece of foil.

Combine the olive oil, minced garlic, and chopped rosemary. Generously brush this mixture all over the lamb roast. Make sure to coat all sides.

Season the lamb all over with salt and pepper. Use your hands to evenly distribute the oil and herb mixture and help it adhere.

Wrap the seasoned roast tightly in the foil. Marinate it in the fridge for 1-2 hours, or up to overnight. This allows the flavors to penetrate deep into the meat.

Step 2 – skewer the roast

Remove lamb from the fridge for about 30 minutes before grilling. Take it out of the foil.

Skewer the roast lengthwise through the middle using 4-5 metal or soaked wooden skewers. Space them evenly to keep the roast straight and allow for even cooking.

Use butcher’s twine to tie the roast at 1-2 inch intervals if needed to hold its shape. Make sure skewers are secure.

Step 3 – prepare the grill

For charcoal, ignite your coals and let them get hot and ashy before grilling. Use enough to create medium heat across the whole grill surface.

For gas, preheat your grill to medium-high. Clean the grates and brush lightly with oil to prevent sticking.

The grill should maintain a temperature around 375-400°F – hot enough to sear the meat but not burn it.

Step 4 – grill the roast

Carefully place the skewered lamb directly over the heat. Let it sear untouched for 2-3 minutes until grill marks form.

Rotate the skewers 90 degrees to create crisscross grill marks. Sear for another 2 minutes. Use tongs to hold skewers, not the meat.

Flip the roast and repeat, searing on the second side—2–3 minutes per side. This caramelization gives it incredible flavor.

Move the roast to indirect heat or turn down one grill burner to create a cooler zone.

Insert a meat thermometer into the thickest part of the lamb, avoiding the bone, so you can maximize its use. Close the grill lid.

Maintain the grill temperature at around 375°F. Let the roast slowly cook until it reaches your desired doneness.

• Rare: 130–135°F
• Medium Rare: 135-145°F
• Medium: 145-150°F
• Well Done: 155°F and above

For medium rare, expect around 15-20 minutes. Check periodically and rotate if needed for even cooking.

Step 5 – make Au Jus (Optional)

For extra juicy and flavorful lamb, you can make an easy au jus sauce as it grills.

In an oven-safe pan, combine 1 cup beef broth, 1 tsp olive oil, 2 cloves minced garlic, and any herb sprigs.

Place the pan under the roast on the grill and let the juices drip down into the broth. Close the lid.

Once the lamb is done, remove the pan and simmer until slightly thickened. Serve this sauce alongside the carved roast.

Step 6 – base and finish

In the last 5 minutes of grilling, start basting the lamb with the rendered fats and juices pooling in the bottom of the grill. Use a brush to coat the roast evenly.

Once it reaches your desired temperature, transfer the roast to a cutting board and tent loosely with foil. Allow it to rest for 10-15 minutes before slicing – this locks in the juices.

Snip off any butcher’s twine. Carefully remove skewers. Carve the rested lamb into thin slices and serve!

Serving Suggestions

This flavorful lamb loin roast pairs wonderfully with all sorts of sides, sauces, and other creative additions:

Grilled vegetables

Grill asparagus, peppers, zucchini, eggplant, etc. right alongside the lamb.

Chimichurri sauce

The fresh Argentine herb sauce adds incredible brightness.

Tzatziki

Cooling Greek yogurt, cucumber, and mint dip.

Couscous salad

Toasted couscous with cucumber, tomato, feta, and herbs.

Polenta

Creamy soft or crispy grilled polenta.

Pita bread

Warm pita, perfect for sopping up lamb juices.

Hummus

Chilled hummus balances the rich meat.

Grilling tips

Use these handy tips for the perfect lamb loin roast every time:

Use indirect heat

Cooking over indirect heat prevents burning while slowly roasting.

Watch temperatures

Use a meat thermometer for precise doneness – remove right at target temp.

Rest the meat

Letting it rest ensures juicy, tender meat that won’t dry out.

Clean grates

Prevent sticking by cleaning grates and brushing with oil before grilling.

Add smoke

Try adding soaked wood chips to gas or charcoal grills for extra smoky flavor.

Create a crust

Searing over direct heat first gives a beautiful browned outside.

Baste late

Basting too early washes away the caramelized crust – wait until nearly done.

Conclusion

Fresh herb-rubbed lamb loin roast hot off the grill makes for an incredible entrée for summer gatherings, camping trips, or anytime you’re cooking outdoors. The hands-on preparation and active grilling time ensure everyone gets involved in the cooking process. Then you can all relax and savor juicy, smoky slices of this impressive roast together.