How to Cook London Broil on the Grill?

How to Cook London Broil on the Grill: grill it for about 8 to 10 minutes total over high heat, flipping once, for a lean steak about 1 inch thick.

Use a thermometer, not the clock, for doneness. London broil is usually a beef steak, so cook it to 145°F (63°C), then rest it 3 minutes. Slice thinly across the grain for the most tender result.

The Short Answer, With Numbers

Grill London broil like a lean beef steak: cook to 145°F (63°C), then rest 3 minutes. That is the USDA safe minimum for beef steaks, chops, and roasts.

Exact Grill Target

For London broil, place the thermometer in the thickest part of the meat. The number that matters is 145°F at the center, followed by a 3-minute rest.

If one end is 1 inch thick and the other is 1 1/2 inches thick, test the thicker end first. Do not average readings. The thickest section must reach 145°F.

For a 2-pound top round London broil, expect uneven thickness. If the thin end reaches the target early, move that end to a cooler part of the grill while the thick end finishes.

A practical setup is a hot side for searing and a cooler side for finishing. Sear both broad faces, then move the meat off direct heat until the center reads 145°F.

Use tongs, not a fork. Piercing the meat is not a safety issue, but it costs juices. London broil is lean, so keeping moisture matters.

Worked Examples

Example 1: The center reads 139°F. Keep cooking. It is not at the safe minimum yet, so do not start the rest period.

Example 2: The center reads 145°F. Remove it from the grill and rest it for 3 minutes before slicing.

Example 3: One spot reads 146°F, but a thicker spot reads 142°F. Keep cooking. The lower thick-spot reading controls the decision.

Example 4: You sliced it and see a cool-looking center. Check the temperature in the thickest remaining piece. If it is under 145°F, return it to the grill.

Slicing and Serving Numbers

After the 3-minute rest, slice London broil thinly across the grain. Aim for slices about 1/4 inch thick, or thinner if the cut seems chewy.

If the grain runs left to right, cut up and down across it. This shortens the muscle fibers, which is the main texture fix for London broil.

For serving size, a 2-pound raw London broil gives about 6 portions if you plan roughly 5 ounces raw weight per person. For larger appetites, plan closer to 8 ounces raw per person.

If marinated, discard used marinade unless it is cooked separately. Do not brush raw-meat marinade onto finished London broil.

The short answer is simple: grill until the thickest part reaches 145°F, rest 3 minutes, then slice thin across the grain.

Choose the Right Cut

Best pick: buy top round steak labeled “London broil,” 1 1/2 to 2 inches thick, weighing 1 1/2 to 2 1/2 pounds. That size grills evenly, slices well, and feeds 4 to 6 people.

London broil is a cooking method, not one fixed cut. In most U.S. meat cases, the package will be top round, flank steak, or sometimes sirloin tip. For grilling, thickness matters more than the label.

Best Cuts for Grilled London Broil

For the most forgiving grill result, choose a steak at least 1 1/2 inches thick. A 2-inch top round gives you time to brown the outside before the center is done.

A thin 3/4-inch “London broil” can overcook in minutes. Use it only if you want a fast cook and can watch it closely. It is better treated like flank steak than a thick London broil.

Look for an even rectangle or oval with consistent thickness. Avoid pieces that are 2 inches thick at one end and 3/4 inch at the other, because the thin end will finish first and dry out.

Choose bright red beef with tight grain and minimal surface liquid. Some marbling is useful, but heavy fat seams are not. London broil is usually lean, so tenderness comes from slicing, not fat.

How Much to Buy

Plan on 6 to 8 ounces raw beef per adult. A 2-pound London broil is 32 ounces raw, enough for about 4 large portions or 5 moderate portions after trimming and moisture loss.

For sandwiches, salads, or meal prep, plan 4 to 5 ounces raw per serving. A 1 1/2-pound steak can make 5 to 6 thinner sliced portions when served with bread, potatoes, or vegetables.

Example: for 6 adults at dinner, buy about 3 pounds total. That can be one large 3-pound steak if thickness is even, or two 1 1/2-pound steaks for easier grilling.

If grilling two steaks, choose matching thicknesses. A 1-inch flank steak and a 2-inch top round will not finish together, even if their weights are similar.

Edge Cases at the Meat Counter

If the only top round is thicker than 2 1/2 inches, ask the butcher to cut it to 1 1/2 to 2 inches. Very thick pieces behave more like small roasts and are harder to grill evenly.

If the only option is a very thin cut, choose flank steak instead of thin top round. Flank has a looser grain and stronger flavor, so it handles quick grilling better.

If tenderness is your top priority, pick top sirloin over top round. It costs more, but it is easier to chew. If classic London broil texture and value matter more, choose top round.

Whichever cut you buy, identify the grain before cooking. London broil must be sliced thinly across the grain after grilling. Even a well-chosen cut will seem tough if sliced with the grain.

For beef steaks, chops, and roasts, the USDA safe minimum internal temperature is 145°F with a 3-minute rest. Use a thermometer; color alone is not a reliable doneness guide.

Marinate for Better Flavor

For grilled London broil, use a marinade that seasons deeply, adds browning, and protects the lean beef from tasting dry. Plan on 1/2 cup marinade per 1 pound of meat.

A typical London broil is 1 1/2 to 2 pounds and 1 to 1 1/2 inches thick. For that size, make 3/4 to 1 cup marinade and use a shallow dish or zip-top bag so all surfaces stay coated.

Use This Ratio

For a 1 lb piece, cut every amount in half. For a 3 lb piece, multiply by 1 1/2. Do not drown the beef; a thin coating works better than a pool because it stays in contact with the surface.

Marinate 4 to 8 hours for the best balance. A 1-inch steak can taste seasoned after 2 hours. A 1 1/2-inch steak benefits from 8 to 12 hours, especially if it is thick at one end.

Do not overdo the acid. Keep acid near 2 tablespoons per 2 pounds of beef. More can make the outer 1/8 inch feel mushy before the center gains much flavor.

How to Marinate Evenly

Score the surface lightly if the cut is thick or tight-grained. Make shallow cuts about 1/8 inch deep in a crosshatch pattern, spaced 3/4 inch apart. Do not cut deeply, or juices escape faster on the grill.

Turn the beef at least once halfway through marinating. In a bag, press out extra air so the marinade touches more surface. In a dish, spoon marinade over the top before covering.

Before grilling, remove the beef from the marinade and blot it with paper towels. Wet meat steams first and browns late. A dry surface gives stronger grill marks in the first 2 to 3 minutes.

Discard used marinade unless it is boiled separately before serving. For an easy sauce, reserve 1/4 cup clean marinade before adding raw beef, then brush it on after slicing.

If your marinade contains a lot of sugar, use medium-high heat instead of the hottest setting. Sugar can darken fast; if the surface chars before the center is ready, move the beef to a cooler grill zone.

London broil is a beef steak, so cook it to at least 145°F and let it rest 3 minutes. Slice across the grain into 1/4-inch strips so the marinade flavor is spread across more cut surfaces.

Prepare the Grill

Set up the grill for very hot direct cooking plus a cooler safety zone. London broil is usually a lean top round steak, so it needs fast browning without a long stay over the flame.

Plan on a grill surface temperature of about 450°F to 550°F for the searing zone. If your grill has a lid thermometer, expect it to read lower or higher than the grate; use it as a guide, not a guarantee.

Gas Grill Setup

Open the lid before lighting. Turn all burners to high and preheat for 10 to 15 minutes. The grates should be hot enough that oil residue smokes lightly after brushing.

For a 3-burner grill, leave the left and center burners on high. Turn the right burner to low or off. That gives you a hot zone for searing and a cooler zone for finishing or holding.

For a 2-burner grill, set one burner to high and the other to low. If the steak is 1 inch thick, it may cook entirely over high heat. If it is 1 1/2 inches thick, the low side matters.

Example: a 1 1/4-inch London broil can sear 4 to 5 minutes per side over high heat, then move to the low side if the center is lagging behind the crust.

Charcoal Grill Setup

Use a 2-zone fire. Fill a chimney about 3/4 full for a standard 22-inch kettle. When the top coals are mostly ashed over, pour them onto one half of the charcoal grate.

Leave the other half empty. This cooler side lets you control flare-ups and avoid burning the outside before the center reaches the target doneness.

Spread the lit coals in an even layer 1 to 2 coals deep on the hot side. Put the cooking grate on, cover, and preheat for 5 minutes with the vents open.

If using lump charcoal, watch for extra-hot spots. Rake tall piles flat before cooking. A London broil sitting over a mound of lump can scorch in under 2 minutes.

Clean, Oil, and Test the Grates

Scrape the grates after preheating, not before. Heat loosens stuck-on food. Use a grill brush or a crumpled sheet of heavy foil held with tongs.

Oil the food, not the fire. Brush the steak lightly with about 1 teaspoon oil per pound. Oiling the grate heavily can drip, flare, and leave bitter soot on lean beef.

To test heat without a thermometer, hold your palm 3 inches above the grate. A 2-second hold suggests high heat. A 4-second hold suggests medium-high heat.

If flames jump when the steak goes down, move it to the cooler zone for 30 to 60 seconds. Let the flare die, then return it to the hot zone to keep searing.

Target Temperature Planning

London broil is a beef steak, so the USDA safe minimum internal temperature is 145°F with a 3-minute rest. Use an instant-read thermometer in the thickest part.

Because thin lean steaks climb quickly, start checking early. For a 1-inch steak, check after about 8 minutes total. For a 1 1/2-inch steak, check after about 10 minutes total.

If the outside is dark but the center is not ready, stop direct grilling. Move the steak to the cooler zone, close the lid, and check again every 2 minutes.

If the grill is running weak, extend the preheat. A steak placed on lukewarm grates steams first, sticks more, and loses the browned crust that London broil needs.

Grill London Broil Step by Step

Use this method for a 1 to 1 1/2-inch-thick London broil, usually top round or flank-style beef. The target is a browned outside, a pink center, and a verified 145°F internal temperature with a 3-minute rest.

Direct-then-indirect grilling method

• Step 1: Trim and season. Pat the beef dry. Trim thick surface fat to about 1/8 inch. Salt with 3/4 teaspoon kosher salt per pound, plus 1/2 teaspoon black pepper. For a 2-pound London broil, use 1 1/2 teaspoons salt.
• Step 2: Preheat for two zones. Heat one side of the grill to high, about 450°F to 500°F at the grate. Leave the other side unlit or low. Scrub and oil the grate so the lean beef releases cleanly.
• Step 3: Sear the first side. Place the meat over direct high heat. Grill 3 to 4 minutes without moving it. Rotate 45 degrees halfway through only if you want crosshatch marks; otherwise leave it alone for better browning.
• Step 4: Sear the second side. Flip once and grill the second side 3 to 4 minutes. A 1-inch piece may already be close to done. A 1 1/2-inch piece usually needs more time over indirect heat.
• Step 5: Finish indirectly. Move the beef to the cooler side. Close the lid and grill 2 to 6 minutes more, depending on thickness. Start checking at 8 total minutes for 1 inch, and at 10 total minutes for 1 1/2 inches.
• Step 6: Check the center. Insert an instant-read thermometer through the side into the thickest part. London broil must reach 145°F, then rest 3 minutes. If it reads below 145°F, return it to indirect heat and recheck every 1 to 2 minutes.
• Step 7: Rest and slice thin. Rest on a board for 3 minutes. Slice across the grain into 1/8 to 1/4-inch strips. If the grain changes direction, rotate the meat and keep slicing across the visible muscle lines.

Timing examples

If the outside is getting too dark before the center reaches 145°F, move it fully to indirect heat and close the lid. If the center is done but the surface is pale, give it 30 to 45 seconds per side over high heat.

For a gas grill, keep the lid closed during indirect cooking. For charcoal, bank coals on one side and place the meat opposite the coals. On windy days, expect the indirect stage to take 2 to 4 minutes longer.

Slice and Serve Correctly

Move the grilled London broil to a cutting board and rest it at least 3 minutes if it has reached 145°F. That USDA figure applies to beef steaks, chops, and roasts.

For best slicing, rest longer than the safety minimum: 8 to 10 minutes for a 1-inch-thick piece, or 10 to 15 minutes for a 1 1/2-inch piece. Keep it uncovered or loosely tented.

Do not slice straight off the grill. A 2-pound London broil cut immediately can lose several tablespoons of juice onto the board, leaving the center drier by the time it reaches the plate.

Find the Grain Before You Cut

London broil is usually flank steak, top round, or another lean cut. These muscles have long fibers. Your main job is to cut those fibers short.

Look for parallel lines running across the surface. That direction is the grain. Turn the meat so your knife crosses those lines at a 90-degree angle.

If the grain runs left to right, slice front to back. If it runs front to back, slice left to right. If it changes direction, cut the steak into sections first.

Worked example: a 10-inch-long flank steak may have grain running lengthwise. Cut it crosswise into 2 or 3 shorter blocks, then slice each block across the grain.

For top round, the grain can curve. Start at one end, slice 3 or 4 pieces, then rotate the remaining meat as the lines change.

Slice Thin, Then Serve Fast

Use a sharp slicing knife, not a serrated bread knife. Hold the knife at a slight 30- to 45-degree angle to make wider, thinner slices.

Aim for 1/8-inch slices for sandwiches, salads, and tacos. Use 1/4-inch slices for dinner plates. Avoid 1/2-inch slabs; they chew tough even when cooked correctly.

Example: a 1 1/2-pound London broil sliced 1/4 inch thick yields about 18 to 24 slices, depending on shape. At 1/8 inch, expect roughly 35 to 45 slices.

For a platter, overlap slices in a single shingled layer. Spoon any board juices over the top. Add a small pinch of coarse salt only after tasting.

If the first slice looks too rare for your preference, do not microwave the whole steak. Put only the cut slices back on the hot grill for 30 to 60 seconds per side.

If the meat seems firm or dry, slice thinner. A 1/8-inch cut across the grain can make a lean top round noticeably easier to chew than a 1/4-inch cut.

For sandwiches, cut long slices in half before stacking. Pieces about 3 to 4 inches long bite cleanly and do not pull out of the bread.

For steak salad, cut slices into 2-inch strips after slicing across the grain. This keeps each bite tender without making the meat look chopped.

If serving family-style, slice only what will be eaten in the first 10 minutes. Keep the remaining piece whole, then slice more as needed to reduce drying.

Reheated leftovers should reach 165°F. Warm sliced London broil gently with a splash of broth or pan juices, then serve as sandwiches, rice bowls, or tacos.

Frequently Asked Questions

What temperature should London broil reach on the grill?

Cook London broil to a safe minimum internal temperature of 145°F, measured in the thickest part with a food thermometer. Let it rest for 3 minutes before slicing. Because London broil is usually lean, slicing thinly across the grain helps keep it tender.

How long does London broil take on the grill?

For a 1 to 1 1/2-inch-thick London broil, grill about 5 to 7 minutes per side over medium-high heat, then check with a thermometer. Time varies by thickness and grill heat. The target is 145°F with a 3-minute rest.

Should I marinate London broil before grilling?

Yes. Marinate London broil for better flavor and tenderness, especially because it is a lean cut. Use an acidic marinade with oil, salt, garlic, and pepper. Before grilling, pat the surface dry so it sears instead of steaming.

Do you grill London broil with the lid open or closed?

Grill London broil with the lid closed most of the time to maintain steady heat. Sear it over medium-high heat, flip once, and use a thermometer instead of guessing. Remove it when it reaches 145°F, then rest it for 3 minutes.

How do you slice London broil after grilling?

After the 3-minute rest, slice London broil thinly across the grain. Look for the direction of the muscle fibers, then cut perpendicular to them. Aim for slices about 1/4 inch thick. This matters as much as cooking temperature for tenderness.

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