To grill a london broil steak, marinate, sear hot, cook to 130–145°F, rest, and slice thinly against the grain.
London broil looks like a big, tough slab of beef, but handled the right way it turns into a tender steak with deep flavor and a juicy pink center. The trick is simple: a smart marinade, solid grill setup, and a bit of patience with resting and slicing.
This guide walks you through every step, from picking the right cut to getting the doneness you like. You will see how to set up your grill, how long to marinate, when to flip, and how to avoid dry or chewy meat.
What Is London Broil Steak?
In most stores, “London broil” describes a way to cook and slice a lean cut, not a specific muscle from the cow. Butchers often label top round or flank steak as London broil. Both cuts are lean, with strong grain lines and very little marbling, so they need high heat and thin slicing.
Top round tends to be thicker and a bit firmer. Flank is flatter with a looser grain and can feel slightly more tender when sliced across the grain. Either one can wear the London broil label, and both work well on a hot grill when handled with care.
London Broil Grill Planning At A Glance
Use this cheat sheet early on so you match the cut, thickness, and timing before you even fire up the grill.
| Factor | Typical Range | Quick Note |
|---|---|---|
| Cut Labeled “London Broil” | Top round or flank steak | Both are lean; slicing matters more than fat. |
| Average Weight | 1½–2½ pounds | Heavier pieces need longer marinating and finishing time. |
| Typical Thickness | 1–2 inches | Thicker steaks need lower finishing heat after the sear. |
| Marinating Time | 4–24 hours in fridge | Longer for top round, shorter for thinner flank. |
| Searing Heat | 450–550°F grill grate | High heat gives color without cooking the center too fast. |
| Target Internal Temp | 130–145°F for serving | USDA minimum is 145°F with a short rest for safety. |
| Resting Time | 10–15 minutes | Juices settle so slices stay moist. |
| Slicing Direction | Across the grain, thin slices | Turns a lean, firm cut into tender bites. |
How To Grill A London Broil Steak For Tender Results
This section lays out a simple, repeatable method that you can follow every time you want to know how to grill a london broil steak for a weekend cookout or a quick weeknight dinner.
Step 1: Choose And Trim The Steak
Look for a London broil that feels firm but not rock hard and has a deep, rich color. Avoid pieces with a rainbow sheen or a strong sour smell. A thickness between 1¼ and 1¾ inches hits a sweet spot for grilling: thick enough to stay juicy, thin enough to cook through without a long wait.
Pat the steak dry with paper towels. Trim off any thick surface fat or silver skin. This keeps the marinade in touch with the meat itself and helps the steak cook evenly over the grill grates.
Step 2: Mix A Marinade That Works
London broil loves a marinade with three parts: acid, fat, and flavor. Acid softens the outer layers of muscle, oil carries fat-soluble flavors, and seasonings set the style. A simple base looks like this:
- Acid: red wine vinegar, balsamic, or lemon juice
- Fat: olive oil or another neutral oil
- Flavor: garlic, pepper, dried herbs, soy sauce, Worcestershire, or chili flakes
Use just enough acidity to loosen the meat, not so much that the surface turns mushy. A rough ratio of one part acid to three parts oil with salt and flavorings gives a balanced marinade that treats the steak gently.
Step 3: Marinate Safely
Place the steak in a shallow glass or stainless dish, or in a heavy zipper bag, and pour the marinade over it. Press out extra air and seal. Turn the steak so every part gets coated, then move it straight into the fridge. Cold marinating keeps the meat out of the “danger zone” where bacteria grow fastest.
Let flank steak sit 4–12 hours and thicker top round 8–24 hours, turning once or twice when you open the fridge. Discard used marinade once you remove the meat, or boil it hard if you plan to turn it into a sauce so any germs are destroyed.
Step 4: Bring The Steak To Grill-Ready State
About 30 minutes before grilling, take the steak out of the fridge. Set it on a tray on the counter while you heat the grill. This short pause takes the chill off the surface so the outside browns faster once it hits the hot grates.
Lift the steak from the bag, let extra marinade drip off, and pat the surface dry. A dry surface browns better and avoids flare-ups. Season both sides with a bit more salt and pepper if the marinade was mild.
Setting Up The Grill For London Broil
London broil shines with a two-zone fire: one side hot for searing, one side medium for finishing. This setup gives you color and crust without burning the exterior or leaving the center raw.
Two-Zone Setup On A Gas Grill
Turn one or two burners to high and leave the other burner on low or even off, depending on how many burners you have. Close the lid and let the grill preheat until the hot side hits at least 450°F. If your grates are dirty, scrape them clean while the grill heats so the steak does not stick.
Oil the grates lightly just before the steak goes on. Fold a paper towel, dip it in oil, and sweep it across the bars with tongs. Avoid heavy oiling, which can drip and flare.
Two-Zone Setup On A Charcoal Grill
Light a full chimney of charcoal and pour the glowing coals on one half of the grill. Spread them in an even mound, then leave the other half with no coals under the grate. Adjust top and bottom vents halfway open so the hot side runs near steak-searing range.
Let the grate heat for 5–10 minutes, then clean and oil it as you would with a gas grill. The coal side will be your sear zone; the empty side will be your cooler zone for finishing.
Grilling: Sear, Finish, Rest, Slice
Once your grill is hot and the steak is dry and seasoned, you are ready to cook. This is where the magic happens for anyone learning how to grill a london broil steak without overcooking it.
Sear Over High Heat
Lay the steak on the hot side of the grill. You should hear a strong sizzle right away. Close the lid and leave the steak undisturbed for 3–5 minutes, depending on thickness. Lift and check for deep brown grill marks rather than a pale surface.
Flip and sear the second side for another 3–5 minutes. If flare-ups shoot up around the fat edges, slide the steak briefly toward the cooler zone until the flames settle, then move it back.
Finish Over Medium Heat
After the sear, move the steak to the cooler side of the grill. Insert a digital thermometer into the thickest part from the side so the tip lands near the center. Close the lid and let the steak cook gently until it is about 5°F below your target final temperature.
For people who like a pink center and extra safety margin, aim to pull the steak between 140°F and 145°F, then let it rest. That lines up with food safety charts that recommend at least 145°F with a short rest for whole cuts of beef.
Rest Before Slicing
Move the steak to a cutting board and tent it loosely with foil. Let it rest for 10–15 minutes. During this time, juices move back through the meat and the temperature evens out from edge to center. The reading will usually climb a few degrees while it rests.
Skip cutting during this stage. If you slice too soon, the juices run out and the lean cut dries quickly, no matter how well you marinated it.
Slice Thinly Across The Grain
Find the grain lines in the steak. On flank they run in one clear direction; on top round they may angle across the surface. Position your knife so you cut across those lines, not with them. Use a sharp carving or chef’s knife and slice into thin, quarter-inch slices.
Angle the blade slightly as you cut so each slice has a broad face. That gives the impression of thicker steak while still keeping the bite tender enough for a lean muscle.
Marinades, Dry Rubs, And Seasoning Ideas
Once you have the basic method down, you can swap flavors to suit whatever you want to serve alongside the steak. London broil handles bright acid, savory soy, and big spice blends without losing its beefy taste.
Classic Garlic And Herb Marinade
Combine olive oil, red wine vinegar, minced garlic, dried oregano, black pepper, and a spoon of soy sauce. This mix suits top round that needs more help with tenderness. The soy adds both salt and umami, while the herbs cling to the surface and toast on the grill.
Citrus And Chili Marinade
For a lighter twist, mix orange juice, lime juice, oil, garlic, and crushed red pepper. Citrus brightens the meat and pairs well with grilled vegetables and fresh salsa. Keep acidic marinades under about 12 hours so the surface does not turn soft.
Dry Rub For Quick Flavor
If you do not have marinating time, pat the steak dry, brush it with a little oil, and coat it in a rub of kosher salt, coarse black pepper, smoked paprika, onion powder, and a hint of brown sugar. Let it sit on the counter for 20–30 minutes while the grill heats so the salt can sink in a bit.
Food Safety And Doneness For London Broil
Lean beef does not forgive sloppy temperature control. A thermometer and safe handling habits keep the meat tasty and safe for everyone at the table.
Safe Internal Temperatures
Food safety agencies advise cooking whole cuts of beef, including steaks and roasts, to at least 145°F and then letting the meat rest for a few minutes. At that point, germs that cause illness are reduced to safe levels while the meat still holds a pink center if you avoid overcooking on the grill.
Many steak fans enjoy London broil a bit lower, around 130–135°F, which lands in the medium-rare range. If you go that route, use fresh meat, chill it properly before cooking, and limit how long it stays in the temperature “danger zone” between 40°F and 140°F.
Safe Marinating Habits
Always marinate London broil in the fridge, never on the counter. Cold storage slows bacterial growth and keeps the meat in a safe range. Non-reactive containers like glass, ceramic, stainless steel, or food-safe plastic work well with acidic marinades.
Do not reuse marinade that has touched raw meat unless you boil it hard first. If you want a finishing sauce, set some of the marinade aside before you pour the rest over the steak, or simmer the used marinade for at least a minute at a full boil.
Common London Broil Grill Errors And Fixes
Even experienced grillers sometimes end up with chewy or dry London broil. Most problems trace back to a short list of habits that are easy to fix once you know what to watch.
Steak Turns Out Tough
If each bite takes a lot of chewing, the steak may have been sliced with the grain or it never had enough marinating time. Adjust by marinating longer next time, aiming for the upper end of the range for thick top round, and always slice thinly across the grain.
Dry, Gray Interior
Dry meat often means too much time over direct high heat or cooking far past your target temperature. Use the two-zone setup so you can move the steak to the cooler side after the sear, and rely on a thermometer instead of guessing by color alone.
Bitter, Burned Outside
Sweet or sugary marinades burn fast on a hot grill. Lower the searing heat slightly, pat the steak dry before grilling, and move it away from open flames. You can brush on a fresh glaze near the end of cooking as long as that glaze has not touched raw meat.
Uneven Doneness
If the thin end dries while the thick center stays underdone, angle the thicker end closer to the hot side and the thinner end toward the cooler zone during the finishing stage. You can also cut a large London broil in half crosswise and remove the thinner piece sooner.
London Broil Grill Time And Temp Reference
Use this table as a starting point. Actual times still depend on grill type, weather, and how steady your fire runs, so always confirm with a thermometer.
| Thickness | Direct Sear Time (Per Side) | Approx. Finish Time To 140–145°F |
|---|---|---|
| 1 inch | 3–4 minutes | 2–5 minutes over medium heat |
| 1¼ inches | 4–5 minutes | 4–7 minutes over medium heat |
| 1½ inches | 5 minutes | 6–10 minutes over medium heat |
| 1¾ inches | 5–6 minutes | 8–12 minutes over medium heat |
| 2 inches | 6 minutes | 10–15 minutes over medium heat |
| Resting Time | 10–15 minutes under loose foil after grilling | |
| Slicing | Thin slices across the grain for tender bites | |
Serving Ideas For Grilled London Broil
Once the steak is sliced, it fits into a wide range of meals. You can serve it straight from the board with grilled vegetables and potatoes, or fan slices over a simple green salad with a sharp vinaigrette. The lean texture works well in sandwiches on crusty bread with onions and peppers.
Leftover slices keep well in the fridge for a couple of days. Serve them cold over salad, tuck them into tacos with salsa and lime, or reheat gently in a pan with a splash of broth to keep them from drying out.
Bringing It All Together On The Grill
Grilling a London broil steak comes down to a handful of steady habits. Choose a good cut, marinate long enough to soften the outer layers, set up a two-zone fire, sear hot, finish to a safe internal temperature, rest, and slice across the grain. When you repeat that pattern, even a lean, budget-friendly cut turns into steak night that feels special.
The next time you pick up a thick London broil at the store, you will know exactly how to grill a london broil steak that stays juicy and tender from edge to center, with flavor that stands up to any side dish on the table.