How To Grill A London Broil On A Gas Grill: Pro Tips

Sear over high heat, then finish indirect for a tender, juicy London broil every time.

I have grilled dozens of large cuts and taught backyard cooks how to grill a London broil on a gas grill. This guide walks you from choosing the steak to resting and slicing. Expect clear steps, real tips from my own trials, and answers to common problems so you can cook with confidence.

What is London broil and why grill it on gas

London broil is not a cut name but a cooking method. It usually uses top round or flank steak. These muscles are lean and flavorful. A gas grill gives steady heat and easy control. That makes it ideal for how to grill a London broil on a gas grill.

I prefer gas for fast sear and easy indirect finishing. My first try burned the outside and left the inside tough. After tweaking temperature and rest time, the meat improved. You will learn those tweaks here.

Choosing the right cut and size

Pick a cut that suits the London broil method. Look for:

• Top round roast 1.5 to 3 pounds for classic London broil.
• Flank steak for faster cook time and bold grain.
• Flat iron for a more tender result if you want less chew.

Choose a steak about 1 to 1.5 inches thick for even cooking. Thinner steaks cook too fast. Thick ones need longer indirect heat. Trim excess fat, but leave a thin cap for flavor.

Tools, ingredients, and prep checklist

You need simple tools and pantry staples. Prepare them before you grill.

• Gas grill with at least two burners and a lid.
• Instant-read thermometer for accuracy.
• Tongs, long spatula, and a clean cutting board.
• Olive oil, kosher salt, black pepper, garlic, and citrus or vinegar for acid.
• Optional: a meat mallet, coarse sea salt, and fresh herbs.

Allow the steak to come to room temperature for 30 to 60 minutes. Pat dry with paper towels. Oil the meat lightly to help sear.

Marinades, rubs, and seasoning tips

Marinade helps break down muscle fibers and add flavor. Try a simple acid-based mix.

• Mix 1/4 cup olive oil, 2 tablespoons soy sauce, 2 tablespoons lemon juice, 2 cloves minced garlic, and 1 teaspoon black pepper.
• Marinate for 2 to 6 hours in the fridge. Do not marinate more than 8 hours or meat can get mushy.
• For a dry rub, use kosher salt, cracked black pepper, garlic powder, and a touch of smoked paprika.

Salt at least 30 minutes before grilling for better crust. I once over-salted and masked the beef flavor—so salt with care.

Gas grill setup and temperature control

A good setup makes or breaks the cook. Use two heat zones.

• Turn one burner to high and the other to medium-low or off to create direct and indirect zones.
• Aim for a searing zone at 500°F and an indirect zone between 300°F and 350°F.
• Clean and oil the grate before you start to prevent sticking.

Close the lid while finishing on indirect heat. I learned to trust the thermostat and my instant-read thermometer more than guesswork.

Step-by-step: how to grill a London broil on a gas grill

Follow these clear steps for reliable results.

• Preheat the grill for 10 to 15 minutes until the searing zone is hot.
• Sear the steak over direct heat for 2 to 4 minutes per side to get a good crust.
• Move the steak to the indirect zone and close the lid.
• Cook until the internal temp reaches your target:
  • 125°F for rare
  • 135°F for medium-rare
  • 145°F for medium
• Remove the steak 5°F below your target temperature. Carryover heat raises temp after you pull it.
• Rest the steak for 10 to 15 minutes under foil to lock juices.
• Slice thinly across the grain at a 45-degree angle.

Repeat the phrase: if you wonder how to grill a London broil on a gas grill, these steps cover sear, indirect finish, and rest. In my tests, a 2-pound top round reached medium-rare in about 12 minutes total with this method.

How to read internal temperature and timing

Temperature is king for consistent doneness. Use an instant-read probe to avoid guesswork.

• Insert probe into the thickest part, away from bone or fat.
• Check at the end of indirect time, not during sear.
• Expect a 5°F rise while resting. Pull early to avoid overcook.

Times vary with thickness. For a 1-inch flank, sear 3 minutes per side and 6 to 8 minutes indirect. For a 1.5-inch top round, sear 4 minutes per side and 8 to 12 minutes indirect.

Resting, slicing, and serving

Resting makes the final dish juicy. Keep steps simple.

• Rest for 10 to 15 minutes tented loosely with foil.
• Slice against the grain in thin slices to break muscle fibers.
• Serve with chimichurri, creamy horseradish, or simple pan juices.

I like to finish with flaky sea salt and a squeeze of lemon. It brightens the rich beef.

Common mistakes and troubleshooting

Avoid these common traps when you learn how to grill a London broil on a gas grill.

• Mistake: Skipping room temp. Cold meat cooks unevenly.
• Mistake: Over-marinating. Acid can make texture mushy.
• Mistake: Cutting too soon. You lose juices if you slice early.
• Mistake: Cooking only on direct heat. The outside chars before the center cooks.

If your steak is tough, try pounding thin, marinating longer, or slicing thinner across the grain.

Personal experience and lessons learned

I once hosted a family cookout and overcooked a top round. It was dry and chewy. After that, I changed my method.

• I started using a two-zone grill setup.
• I bought a better instant-read thermometer.
• I began resting all steaks 10+ minutes before slicing.

Those small changes made the steak juicier and the guests happier. Treat the process like a recipe you can refine.

Serving ideas and side pairings

Pair simple sides that balance the meat. Keep flavors bright and textural.

• Grilled vegetables like asparagus or bell peppers.
• A light salad with citrus or vinegar dressing.
• Roasted potatoes or creamy polenta.
• Sauces: chimichurri, mustard sauce, or gremolata.

These sides complement the beef without masking how to grill a London broil on a gas grill.

Frequently Asked Questions of how to grill a london broil on a gas grill

What cut should I buy for London broil on a gas grill?

Top round and flank steak are common choices. Top round gives a classic roast feel, while flank is lean and has bold grain.

Can I cook London broil directly over high heat only?

No. You need direct heat to sear and indirect heat to finish. Direct-only often chars outside and leaves the center undercooked.

How long should I marinate a London broil?

Marinate 2 to 6 hours for best flavor and texture. Avoid over-marinating more than 8 hours, which can soften the meat too much.

What internal temperature is best for medium-rare?

Aim for 130°F to 135°F as your pull temp, then rest for 5 to 10 minutes. The temp will rise about 5°F during rest.

How thin should I slice London broil after grilling?

Slice very thin, about 1/8 to 1/4 inch, against the grain. Thin slices make even a lean cut feel tender and easy to chew.

Conclusion

You can master how to grill a London broil on a gas grill with a few simple steps: pick the right cut, season well, sear hot, finish indirect, and rest before slicing. Small shifts in heat control and timing make a big difference. Try the method once and tweak it to match your grill and taste. Share your results, ask questions, or subscribe for more step-by-step grill guides.