Not necessarily, london broil is a value label for lean beef, usually flank steak (IMPS 193) or top round (IMPS 169), that turns chewy only when you overcook it, skip the marinade, or slice it the wrong way. The muscles used for those cuts work hard during the animal’s life, so the meat arrives with long, tight fibers and almost no intramuscular fat. Cook it like a cheap steakhouse cut and you will chew rubber; cook it like the lean roast it is, with acid, salt, low internal temperature, and a sharp knife across the grain, and it becomes one of the most rewarding weeknight roasts in your rotation.
This guide covers what the label actually means, why the meat turns chewy, the prep steps that set you up to win, the right cooking temperatures and times, and how to slice and store what is left so it stays tender the next day.
What ‘London Broil’ Actually Means at the Butcher Counter
The phrase on the package is a marketing and preparation term, not a specific muscle. In the United States, most grocery stores label either flank steak or top round as london broil, and in some regions you will see bottom round rolled and tied under the same banner. The Beef Checkoff and the USDA do not regulate “london broil” as an official cut name, which is why the same label can sit on two very different roasts at two different stores.
Both common cuts share the same problem: long muscle fibers and very little marbling. Flank is broad, flat, and about 1 inch thick, harvested from the abdominal wall, while top round is a rump roast cut into a thick, lean steak. A USDA Choice top round carries slightly more fat flecked through it than a USDA Select version, which makes it marginally more forgiving, but neither cut rewards high heat and long cooking the way a ribeye does.
Flank Versus Top Round at a Glance
| Feature | Flank Steak (IMPS 193) | Top Round (IMPS 169) |
|---|---|---|
| Typical thickness | 0.75 to 1 inch | 1 to 1.5 inches |
| Best for | Marinated, hot-seared, sliced thin | Roasted, butterflied, or braised |
| Flavor intensity | Beefy, slightly mineral | Mild, lean, classic roast flavor |
| Marbling | Very low | Low to moderate, depending on grade |
| Forgiving range on the thermometer | Rare to medium-rare only | Rare to medium with quick sear |
Why London Broil Turns Out Tough and Chewy
The complaint almost always comes down to a few predictable mistakes. Lean beef has very little internal fat to baste itself as it cooks, so every degree past medium-rare squeezes more moisture out of the muscle and tightens the protein into something that resists your teeth. If you have ever chewed a piece and watched the juice run onto the plate instead of staying in the bite, that is the issue: water left the meat during cooking, and you cannot get it back at the table.
A second cause shows up before the pan even heats. Without an acidic or enzymatic marinade, the long fibers stay bunched together, and salt never has time to dissolve the muscle proteins into a tender gel. A third cause hides in plain sight at the end: slicing with the grain instead of across it. Even a perfectly cooked roast feels chewy when the knife runs parallel to those visible lines. A fourth cause is thermal shock from the fridge. A cold hunk of meat hitting a screaming-hot pan cooks unevenly, drying the outer half while the center stays cool.
The Four Usual Suspects
- Overcooking past medium: the single biggest reason home cooks get shoe-leather results.
- Skipping the marinade: acid and salt need hours, not minutes, to soften tight fibers.
- Slicing with the grain: every cut doubles in perceived toughness when left long.
- Cold steak on hot heat: the interior dries out chasing the exterior crust.
Choosing a Cut, Marinade, and Prep Plan That Sets You Up to Win
Start at the counter, not at the stove. Ask the butcher which cut is wrapped under the london broil label today, and pick flank for a bold marinade or top round if you want a thicker roast that can hold a classic sear-and-roast treatment. A flank cut will reward a long soak in an acidic mixture; a top round will reward a dry brine of plain salt for 45 minutes to an hour before it ever meets a marinade.
A solid marinade runs four parts: an acid like red wine vinegar, citrus juice, or yogurt; an oil such as olive or avocado; salt; and aromatics like garlic, soy sauce, rosemary, or Worcestershire. Soak for at least 4 hours, ideally overnight in the refrigerator, in a zip-top bag laid flat so the liquid touches every surface. Before you sear, lift the meat out, blot it dry with paper towels, and let it sit on the counter for 20 to 30 minutes so the chill comes off. Score any thick section lightly with a sharp knife or tenderize it gently with a meat mallet to even out the thickness, and you have erased three reasons for toughness before the heat is on.
Pat the surface bone-dry before the sear. A wet steak steams in its own moisture and never builds the brown crust that carries half the flavor.
Building a Marinade That Actually Tenderizes
Acid does the heavy lifting by breaking down surface proteins, salt helps them relax and hold moisture, and oil carries fat-soluble flavors deep into the meat. Yogurt-based marinades add lactic acid plus calcium, which together collapse protein structure faster than vinegar alone. Whatever formula you pick, keep the meat submerged and the fridge door closed until it is time to cook.
Cooking Temperatures and Times for a Tender Result
The target window for lean london broil cuts is 125 to 130 degrees F internal temperature for medium-rare, pulled early because the temperature will climb another 5 to 10 degrees during the rest. Anything past 140 degrees F is asking for trouble. A reliable instant-read thermometer is the difference between a tender roast and a leather belt, and a tool like a Thermapen or ThermoPro makes this step almost foolproof.
Cook hot and fast. A two-zone charcoal or gas fire, with coals or burners blazing on one side and a quiet zone on the other, lets you sear for 90 seconds per side over direct heat and then slide the meat to the cool side to finish gently with the lid closed. In a kitchen, a screaming-hot cast iron pan with a tablespoon of avocado oil works the same way. Plan on roughly 4 to 5 minutes per side for a 1-inch flank, and 6 to 8 minutes total for a butterflied top round, adjusting for thickness. Pull the roast at 125, tent it loosely with foil, and let it rest for 8 to 10 minutes before the knife comes out.
Quick Reference for Doneness
| Pull Temperature | Final Doneness After Rest | Texture on Lean Cuts |
|---|---|---|
| 120 degrees F | Rare | Very tender, cool red center |
| 125 to 130 degrees F | Medium-rare | Tender, warm pink center, ideal |
| 135 to 140 degrees F | Medium | Firmer, less juicy, still acceptable |
| 145 degrees F and up | Well done | Dry, tough, avoid on lean beef |
Slicing, Serving, and Saving Leftovers the Right Way
Look at the cooked roast and you will see thin lines running across it: the muscle fibers. Slice perpendicular to those lines, on a slight bias, into quarter-inch pieces. A long slicing knife like a 10-inch chef’s knife or a Granton-edge slicer makes cleaner cuts than a serrated blade, which tends to tear lean meat. Cutting on the bias shortens each fiber further, doubling the perceived tenderness in every bite.
Slice only what you plan to eat right now. Storing the leftovers whole, wrapped in foil or in a shallow airtight container with a few tablespoons of beef broth or au jus, keeps the unsliced roast from drying out. Reheat gently in a covered skillet with a splash of broth over low heat, or chop cold slices into steak sandwiches, salads, or stir-fries where brief contact with heat keeps them juicy.
Best Uses for Leftover London Broil
- Philly-style sandwiches: sliced thin, warmed with onions and peppers on a hoagie roll.
- Steak salads: served cold over greens with a sharp vinaigrette.
- Beef stir-fry: tossed in at the last second with soy, ginger, and scallions.
- Taco filling: chopped, seasoned with cumin and lime, piled into warm tortillas.
Common Mistakes and Smart Swaps When London Broil Still Fights Back
If your past results have been consistently chewy, walk back through the cook and find the leak. Cooking past medium is by far the most common cause, followed by skipping the rest and slicing with the grain. Crowding the pan is another quiet saboteur: steam builds between the pieces, the surface never browns, and the meat ends up gray and rubbery. A salt-only dry brine of 45 minutes before the marinade is a free upgrade that many cooks skip entirely; it seasons the meat deeply and helps it retain moisture during the sear.
When the cut itself refuses to cooperate, swap it. Skirt steak and flat iron both come from the shoulder area and carry more intramuscular fat than flank or top round, which gives them a wider margin for doneness and shorter marinade times. A Certified Angus Beef flat iron, for example, can roast to medium and still slice tender, a forgiving range that flank rarely matches. America’s Test Kitchen and Cook’s Illustrated have both flagged flat iron as the best weeknight substitute when london broil fights back.
Troubleshooting Chewy Results
- Meat came out dry: you likely overshot 140 degrees F; pull 10 degrees earlier next time.
- Flavor never penetrated: marinate longer, score the surface, or switch to a yogurt-based mix.
- Slices feel rubbery even at rare: the knife followed the grain; rotate your cut 90 degrees.
- No crust formed: the surface was wet or the pan was crowded; pat dry and cook in batches.
Bottom Line
London broil earns its tough reputation for one simple reason: it is a lean cut treated like a forgiving one. A long marinade, a short sear, an internal temperature under 130 degrees F, and a knife that cuts across the grain turn that same package into something genuinely tender. Master those four steps, and the next roast on your table will not just be edible, it will be one of the best steaks you cook all month.
FAQ
Is London broil supposed to be tough?
No. London broil refers to a preparation method applied to lean cuts like flank or top round, and the meat is meant to come out tender when marinated, cooked to medium-rare, and sliced against the grain. Toughness almost always points to overcooking, skipped marination, or wrong-direction slicing.
How do you make London broil tender?
Marinate the meat in an acid-plus-oil mixture for at least 4 hours, sear it hot and fast to an internal temperature of 125 to 130 degrees F, rest it 8 to 10 minutes, and slice thinly across the grain. A 45-minute salt-only dry brine before the marinade adds extra moisture retention.
What is the best way to cook London broil so it is not chewy?
Use a two-zone fire or a cast iron skillet, cook the steak for 4 to 5 minutes per side over direct high heat, pull it at 125 degrees F, and rest it loosely tented before slicing. Quick, hot contact plus an accurate thermometer keeps the lean muscle from tightening past medium.
Why does my London broil come out tough every time?
The two most common causes are overcooking past medium and slicing parallel to the muscle fibers instead of across them. A third is skipping the marinade, which leaves the lean cut without acid to soften tight fibers before the heat arrives.
Should you marinate London broil to make it less tough?
Yes. Marinating is one of the most reliable tenderizing steps for this cut because it adds acid, salt, and flavor that the lean muscle cannot supply on its own. Aim for 4 to 12 hours in the refrigerator for flank, and at least 45 minutes for top round.
What cut of beef is London broil actually from?
Most U.S. grocery stores sell london broil as either flank steak (IMPS 193) or top round (IMPS 169), depending on the region and the supplier. The label is a marketing term, not an official USDA cut name, so the muscle underneath can change from package to package.
