How to Cook a London Broil on a Gas Grill

London Broil is a term that often confuses grill enthusiasts. Contrary to popular belief, it’s not a cut of meat but rather a cooking method. Traditionally, London Broil involves marinating a lean cut of beef (like flank or top round), grilling it over high heat, and slicing it thinly against the grain. When done right, this technique yields tender, flavorful slices of steak perfect for feeding a crowd or elevating a weeknight dinner.

Grilling London Broil on a gas grill is not only efficient, but it also helps impart a savory, smoky char that balances the bright flavors of the marinade. Whether you’re cooking for family or impressing guests, this guide will walk you through every step to cook the perfect London Broil on your gas grill.

Choosing the Right Cut

Since “London Broil” refers to a cooking method rather than a specific cut, selecting the right meat is your first important step. Two of the most popular cuts used for London Broil are:

• Top Round Steak: Lean, affordable, and flavorful when marinated properly.
• Flank Steak: A bit more fibrous, but it grills beautifully and slices into flavorful ribbons.

Some stores may label top sirloin or other cuts as London Broil—what matters most is thickness (1 to 1.5 inches) and grain visibility. Look for a steak that’s evenly shaped and has minimal connective tissue or fat to ensure uniform cooking and tenderness.

Tips for Buying the Right Cut:

• Choose USDA Choice or higher for better marbling.
• Ask your butcher for a fresh, unseasoned cut.
• Avoid overly thin steaks—they’ll overcook before a proper sear.

Prepping the Meat

A. Trimming and Cleaning

Start by rinsing the steak under cold water and patting it dry with paper towels. If there’s excess fat or silver skin (a tough membrane), trim it with a sharp knife. This ensures the marinade penetrates and the steak cooks evenly.

B. Marinating the London Broil

Marination is essential. Because these cuts are lean, they benefit significantly from soaking in an acidic, flavorful marinade. This helps:

• Break down muscle fibers for tenderness.
• Add depth and complexity to the meat.

Basic London Broil Marinade:

• ½ cup olive oil
• ¼ cup soy sauce
• 2 tbsp Worcestershire sauce
• 2 tbsp lemon juice or balsamic vinegar
• 4 garlic cloves (minced)
• 1 tbsp Dijon mustard
• 1 tbsp brown sugar or honey
• 1 tsp dried rosemary
• 1 tsp black pepper
• ½ tsp salt

Mix all ingredients in a bowl. Place the steak in a large resealable plastic bag or glass dish. Pour the marinade over it, seal, and refrigerate for at least 8 hours, ideally overnight (up to 24 hours). Flip occasionally for even coverage.

Preparing the Gas Grill

Before you fire it up, make sure your grill is clean. Use a grill brush to scrape off any old food residue and ash.

Steps to Prepare the Grill:

1. Preheat the Grill: Set burners to medium-high heat (400–450°F). Allow 10–15 minutes for a proper preheat.
2. Two-Zone Setup: Turn off one burner to create an indirect heat zone. This lets you sear the steak first, then finish cooking gently without burning.
3. Oil the Grates: Use tongs and a paper towel dipped in oil to lubricate the grill grates. This prevents sticking and helps with those coveted grill marks.

Grilling the London Broil

A. Bring Meat to Room Temperature

Remove the marinated steak from the fridge 30–45 minutes before grilling. This step promotes even cooking. Pat it dry with paper towels—excess moisture prevents good searing.

B. Searing Over Direct Heat

Place the steak on the hot side of the grill directly over the flames.

• Sear Side 1: Grill for about 4–5 minutes until dark grill marks form.
• Flip and Sear Side 2: Cook another 4–5 minutes on the other side.

Do not press the meat down—you’ll lose juices and dry it out.

C. Finish Over Indirect Heat

Move the steak to the cooler side of the grill and close the lid.

• Continue grilling until the desired doneness is reached.
• Use a meat thermometer to monitor the internal temperature:

Doneness	Internal Temp	Description
Rare	125°F	Very red, soft
Medium-Rare	130–135°F	Warm red center, juicy
Medium	140°F	Pink center, firmer

Avoid going beyond 140°F, as this cut can quickly become dry and chewy.

D. Total Cook Time

Cooking time will vary based on thickness and grill temperature, but expect:

• 10–12 minutes total for a 1.25-inch steak (including searing and finishing)
• Always rely on a thermometer over time alone

Resting and Slicing

A. Resting

Once your steak reaches the desired doneness, remove it from the grill and tent it loosely with foil. Let it rest for 10 minutes. This allows juices to redistribute and makes the meat easier to slice.

B. Slicing the Steak

Use a sharp carving knife and slice the steak thinly against the grain (the lines of muscle fibers you see running through the steak).

Why Cut Against the Grain?

Cutting across the grain shortens the fibers, resulting in a more tender bite. Even if your steak is cooked perfectly, slicing incorrectly can make it feel chewy.

Serving Suggestions

London Broil is incredibly versatile. Its bold, meaty flavor pairs well with both rustic and elevated side dishes.

Great Side Dishes:

• Grilled Vegetables: Zucchini, bell peppers, red onions, and mushrooms
• Baked Potatoes or Roasted Baby Potatoes
• Corn on the Cob with herb butter
• Garlic Bread or crusty rolls
• Fresh Garden Salad with balsamic vinaigrette

Sauces and Toppings:

• Chimichurri: Bright, herby Argentine sauce
• Garlic Herb Butter: Melted over warm steak slices
• Horseradish Cream: Perfect for contrast
• Balsamic Glaze: Adds a hint of sweetness and acidity

For a twist, you can use leftover London Broil in steak sandwiches, wraps, tacos, or even stir-fry dishes.

Tips and Troubleshooting

Tough Steak?

• Ensure a longer marinating time (overnight).
• Always slice thinly and against the grain.
• Don’t overcook; stick to medium or less.

Too Dry?

• Use a thermometer to avoid overcooking.
• Let the steak rest before slicing.
• Consider serving with a moist sauce or glaze.

Uneven Cooking?

• Bring the meat to room temperature before grilling.
• Use two-zone grilling to control heat better.
• Flip only once to allow crust formation.

Steak Sticking to the Grill?

• Clean and oil your grates before cooking.
• Don’t move the steak too soon—once seared properly, it will release naturally.

Conclusion

Grilling a London Broil on a gas grill may seem intimidating at first, but once you understand the method, it’s a straightforward and delicious experience. From selecting the right cut and crafting a bold marinade to mastering the sear and slicing with precision, each step contributes to a tender, flavor-packed result.

To recap:

• Choose top round or flank steak, 1–1.5 inches thick
• Marinate for 8–24 hours
• Preheat grill and sear over direct heat
• Finish cooking over indirect heat to your desired doneness
• Rest and slice thin against the grain

Experiment with marinades, pairings, and presentation to make this meal uniquely yours. Whether it’s a weeknight dinner or a summer backyard feast, London Broil is a satisfying dish that showcases your grilling prowess.