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Herb Mustard Lamb Roast

Featured in Dinner Solutions You'll Love.

Spread mustard-herb blend on lamb, roast hot then slow, let it rest, carve, and top with gravy from pan juices.
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Hannah Author
Updated on Fri, 25 Apr 2025 19:42:26 GMT
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Last Easter I whipped up this mustard-coated lamb roast, and guess what? My mother-in-law wanted my recipe! That's like winning gold at cooking Olympics! The mustard-herb outer layer makes this amazing shell that locks in all the juices. Even folks who aren't big on lamb grab extra helpings.

My lamb-hating brother shocked everyone by eating three servings then casually mentioned he'd love it again when he visits next month.

Ingredients You'll Want

  • Boneless leg of lamb: Go for Australian or New Zealand cuts - they're milder and win over lamb doubters.
  • Dijon mustard: Forms that zingy foundation for your herb coating. Try whole grain if you want some texture.
  • Fresh herbs: Pick up rosemary and thyme - they're lamb's best friends and much better fresh.
  • Garlic: Go heavy handed - its bold taste works wonderfully with lamb.
  • Soy sauce: A tiny bit adds richness without any Asian flavor notes.
  • White wine: Softens the meat and helps build that fantastic pan juice.
  • Good quality olive oil: Makes the coating stick properly and brings extra richness.
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Cooking Steps

Getting Started

Always wipe the lamb completely dry using paper towels before you add the mustard mix. This helps everything stick better and boosts flavor intensity. Don't skip letting the meat sit at room temp - it's crucial for even cooking throughout.

Mustard Mixture

Spread the mustard mix all over your lamb generously, working into every small space. I've learned fingers work best for this job, really rubbing it in. Don't worry about getting messy!

Oven Technique

Start hot to get that outer crust, then drop the temp for perfect cooking. I never trust cooking times - a meat thermometer is a must since lamb costs too much to ruin by overcooking.

Waiting Period

The toughest part? Not cutting in right away! You'll want to, but those 15-20 minutes of rest make the difference between juicy success and dry failure. I loosely tent with foil and finish my side dishes during this time.

I stumbled on the mustard-lamb combo totally by chance when I ran out of mint jelly that usually went alongside. I quickly mixed Dijon with herbs as a backup spread, and it tasted so much better that I started cooking with it directly!

What To Serve With It

This roast goes great with fluffy mashed potatoes or crunchy roasted ones that can soak up the sauce. For veggies, anything green fits perfectly - try roasted asparagus, green beans, or Brussels sprouts for nice color. Add a bottle of red wine (Cabernet Sauvignon or Syrah) and your meal's complete.

Tasty Variations

Mix in a spoonful of honey for a slightly sweet crust. Play with different herbs - mint and oregano give it Mediterranean flair. Want some kick? Stir horseradish into your mustard mix. A bit of lemon zest works wonders to lighten up the flavors too.

Leftovers Plan

Extra lamb makes the best sandwiches next day. Cut it thin, pile on good bread with some arugula and a bit of leftover mustard mix. When warming up, go low and slow around 300°F with foil covering and a splash of broth to keep things juicy.

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Insider Tricks

  • Get your butcher to butterfly the lamb leg so it cooks more evenly
  • For stronger flavor, mix up your mustard coating a day ahead
  • Buy a decent instant-read thermometer as it's the only way to nail perfect doneness

Big cuts of meat used to scare me, especially fancy-sounding lamb. But this dish taught me that sometimes the easiest preparations turn out most impressive. The mustard and herbs do the flavor work, and your oven handles the rest. Now it's my go-to when I want people thinking I slaved away all day, when really I was chilling with wine while it cooked!

Frequently Asked Questions

→ How can I tell if my lamb is medium-rare?
A meat thermometer should read 135°F. Pull it out of the oven and rest for 20-30 minutes.
→ Is it fine to prep this in advance?
You can make the mustard mix a day ahead, but it'll taste best if you coat and roast the same day.
→ What should I serve with lamb?
Mashed potatoes, fresh salads, roasted veggies, or golden potatoes are amazing sides for this dish.
→ Can I replace fresh herbs with dried ones?
Fresh gives the best scent, but you can swap 1 teaspoon each of dried rosemary and thyme if needed.
→ Why do I need to rest the meat after cooking?
Resting helps the meat trap its juices, giving you heavenly and flavorful slices every time.

Mustard Lamb Roast

Boneless lamb leg coated with a mustard mix and fresh herbs, roasted beautifully with savory gravy made from drippings.

Prep Time
30 Minutes
Cook Time
150 Minutes
Total Time
180 Minutes

Category: Main Dishes

Difficulty: Intermediate

Cuisine: Mediterranean

Yield: 8 Servings (1 roast (5 lbs lamb))

Dietary: Low-Carb, Dairy-Free

Ingredients

→ Marinated Lamb

01 1 leg of lamb, boneless (around 5 lbs)
02 1 teaspoon ground ginger
03 1 teaspoon dried rosemary
04 ½ cup mustard (Dijon)
05 2 tablespoons olive oil
06 3 garlic cloves, minced finely
07 1 teaspoon dried thyme
08 2 tablespoons soy sauce

→ Flavor Boosters for Roasting

09 1/2 lemon, cut into slices
10 2 to 4 cups chicken stock
11 A few fresh sprigs of thyme and rosemary
12 1/2 small onion, coarsely chopped

→ Sauce

13 2-4 tablespoons of water
14 Salt and black pepper, to taste
15 ½ cup white wine
16 2 tablespoons regular flour

Instructions

Step 01

Combine Dijon mustard, garlic, soy sauce, ginger, and dry herbs in a bowl. Slowly stir in olive oil until it's creamy and smooth like mayo. Cover the lamb well with this. Set the lamb on a rack (fatty side facing up) inside a roasting tray. Leave it out at room temperature for 2 hours.

Step 02

Switch on your oven and set it to 425°F. Arrange chopped onion, lemon rounds, and some sprigs of fresh herbs beneath the rack in your roasting pan.

Step 03

Put the lamb into the oven for 30 minutes at 425°F.

Step 04

Drop the oven temp to 350°F and resume cooking until your lamb reaches the right internal warmth: about 135°F for medium-rare or 145°F for medium. This'll take roughly another hour and a half. After an hour, pour two cups of your chicken stock into the pan. If it dries up, add a bit more stock after 30 minutes.

Step 05

Pull the meat out of the oven when it's about 5°F under your goal temp. Place it on a board, tent it with foil, and leave it alone for 20-30 minutes.

Step 06

Strain out the fat from the pan juices into a measuring jug, topping it with chicken stock if it comes up short of two cups. Mix together some water and flour to make a slurry. Place your roasting tray on high heat, pour in wine to scrape up those browned bits, and cook it down by half. Add the reserved liquid, stir it in, then whisk in your slurry little by little. Give it a few minutes to bubble until thick. Add salt and pepper last.

Step 07

Snip off the string or net from the lamb. Slice it into portions, then pair each piece with the sauce and enjoy.

Notes

  1. Letting the lamb sit with the marinade before roasting makes the flavor pop.
  2. Take the lamb out of the oven when it's 5°F below your goal temp since it'll keep cooking while resting.
  3. Don’t skip giving the lamb time to rest—it makes it super juicy.

Tools You'll Need

  • Rack with roasting tray
  • Thermometer for meat
  • Foil sheets
  • Strainer tool
  • Whisk for mixing

Allergy Information

Please check ingredients for potential allergens and consult a health professional if in doubt.
  • Includes soy (found in soy sauce)
  • Includes wheat (in soy sauce and flour)

Nutrition Facts (Per Serving)

It is important to consider this information as approximate and not to use it as definitive health advice.
  • Calories: 375
  • Total Fat: 21 g
  • Total Carbohydrate: 5 g
  • Protein: 35 g