Set the top element to 500–550°F, position the rack 4–6 inches below the heat, and cook a 1-inch top round or flank steak about 5 minutes per side for medium-rare. Pull the steak at 125–130°F, rest it 7–10 minutes, then slice thin across the grain so a lean cut eats like a steakhouse special.
This practical walkthrough breaks down broiling London broil in the oven from start to finish, covering the marinade, broiler setup, timing by thickness, and how to pull and slice it for a tender result.
London Broil Is a Method, Not a Cut
“London broil” originally meant a broiled-and-sliced-thin preparation, and most butchers still slap the label on top round or flank steak. Both cuts are lean, muscular, and punishing when overcooked, so the name really describes the technique you apply rather than the steak in your hand.
Top Round vs. Flank: What You’re Actually Holding
Top round comes from the hindquarter and shows a tight, fine grain running along the longer edge. Flank steak sits lower on the belly and has long, obvious muscle fibers you can trace with a fingernail. That visible grain matters at the slicing step, since the cutting direction changes between the two.
Typical Size and Why Uniform Thickness Matters
Most London broil at the supermarket weighs 1.5–2 lb and runs 1–1.25 in thick. A thicker steak gives you a buffer against overcooking the center, while uniform thickness ensures the edges and the middle finish at the same time. If one end flares thin, fold it under and tie with butcher twine so the broiler hits an even surface.
Marinating for Tenderness and Flavor
Lean beef needs a head start because the broiler does not give tough fibers much grace. A wet marinade handles two jobs at once: acid and natural enzymes soften muscle fibers, while oil and salt carry flavor deep into the meat.
The Chemistry Behind a Good Marinade
Vinegar, citrus juice, and wine supply the acid. Papaya and pineapple bring enzymes (bromelain and papain) that actively digest surface proteins. Together they soften the chew without turning the steak mushy. Aim for 4–24 hours of contact time in the fridge; anything under 2 hours barely changes texture.
A Balanced Base Recipe That Works Every Time
Whisk together 1/3 cup olive oil, 1/4 cup soy sauce (or Worcestershire), 3 tablespoons red wine vinegar, 4 smashed garlic cloves, 1 teaspoon dried oregano, 1 teaspoon sugar, and a few grinds of black pepper. Pour over the steak in a zip-top bag, press out the air, and refrigerate. Flip the bag halfway through so both sides soak evenly.
Dry-Brining When a Wet Marinade Isn’t Practical
Salt the steak generously with kosher salt and leave it uncovered on a rack in the fridge for 12–24 hours. The salt draws out moisture, dissolves into it, and gets pulled back into the meat, seasoning it deeply and helping browning once the broiler starts. Pat the surface bone-dry before cooking either way; surface water is the single biggest reason a steak steams instead of sears.
That dry surface also matters when the marinade comes off, so blot thoroughly and let the meat sit briefly before placing it under the heat.
Setting Up the Broiler, Rack, and Pan
The broiler is the hottest thing in your kitchen, and a few minutes of setup decides whether the crust turns mahogany or the whole room fills with smoke. The right rack distance and pan keep fat away from the element and the sear on the meat.
Preheat Fully and Choose the Right Rack Distance
Run the broiler empty for a full 5–10 minutes. A half-warmed element underperforms and slows the sear, which is the opposite of what you want. Position the rack 4–6 in below the element for most ovens. Electric broilers run cooler at the top, so move the rack up to about 3 in; gas broilers run hotter, so drop to 5–6 in. The goal is a fast sizzle the moment the meat hits the heat.
Pick the Right Pan and Skip the Foil Trick
A slotted broiler pan lets fat drip into the lower tray, away from the meat. Set a wire rack inside a rimmed sheet pan as a substitute. Do not line the sheet pan with foil directly under the steak, because dripping fat can ignite, smoke up the kitchen, and leave a metallic taste on the crust.
With fire risk handled, timing becomes the next variable, and a single miscounted minute can swing doneness by a full level.
Pat the steak dry, then season with kosher salt, black pepper, garlic powder, and fresh thyme right before it goes under the broiler. Wet surface + hot element = steam, not sear.
Broiling Times by Thickness and Desired Doneness
The broiler runs on a stopwatch, not a feeling. Thickness drives timing more than weight does, so measure the steak at its thickest point before you start, then plan the flip around the halfway mark.
Thickness-Based Timing Chart
| Steak Thickness | Rare (per side) | Medium-Rare (per side) | Medium (per side) |
|---|---|---|---|
| 1 in | 4 min | 5 min | 6 min |
| 1.25 in | 5 min | 6 min | 7 min |
| 1.5 in | 6 min | 7 min | 8 min |
| 1.75 in | 7 min | 8 min | 9 min |
Flip once at the halfway mark and leave the door cracked an inch for ventilation. If the surface blackens before the center catches up, drop the rack one level rather than lowering oven temperature, which only slows everything and still scorches the outside.
Why You Shouldn’t Move or Baste the Steak
Opening the broiler door to baste or peek drops the cavity temperature and interrupts the crust. The high radiant heat needs uninterrupted contact with the dry surface to build that deep brown sear. Set the timer, walk away, and trust the process until flip time.
Pull Temperatures, Resting, and Carryover Cooking
An instant-read thermometer is the single most valuable tool in this entire process. Cooking by time alone guarantees overcooked gray beef on a steak this lean, since carryover heat keeps climbing long after the steak leaves the broiler.
Pull Temperatures by Doneness
Insert the probe into the thickest part from the side, not the top, to avoid a false reading from surface heat. Pull the steak at 120°F for rare, 125–130°F for medium-rare, and 135°F for medium. The USDA recommends a final internal temperature of 145°F for whole cuts of beef with a 3-minute rest, so most home cooks pull between 135°F and 140°F to land near 145°F after resting.
Resting and the Carryover Math
Transfer the steak to a warm plate or board and tent loosely with foil for 7–10 minutes. During the rest, muscle fibers relax and reabsorb the juices that pushed toward the center during cooking. Expect the internal temperature to climb roughly 5–10°F over that window, depending on thickness and starting temp. That carryover climb is the difference between a perfect medium-rare and an overcooked gray steak.
Once the rest is done, the muscle fibers have reabsorbed their juices, making how you cut across them the final determinant of tenderness.
Slicing Against the Grain and Serving
Slicing turns a properly cooked steak into a tender one or a chewy one. The direction of the cut matters more than the sharpness of the knife, and a few clean strokes save every bite from feeling like a workout.
Identify the Grain and Slice Perpendicular
Look for the long, parallel muscle fibers running along the steak. On flank they run the full length of the piece; on top round they run along the longer edge. Slice perpendicular to those fibers at a slight angle, in thin strips about 1/4 in thick. Cutting across the grain shortens the fibers dramatically and is the single biggest tenderness upgrade available.
Knife Choice and Final Plating
Use a sharp chef’s knife and let the blade do the work with one clean stroke. A serrated blade tears the crust and shreds the meat into ragged strips. Spoon any collected resting juices back over the sliced beef, then finish with chimichurri, a pat of compound butter, or a quick pan sauce made from the broil-pan drippings. Serve over rice, alongside roasted vegetables, or piled into sandwiches with sharp mustard and arugula.
Bottom Line
A great broiled London broil comes down to four checkpoints: dry surface, hot broiler, pull temperature 5–10°F below target, and thin slices cut across the grain. Nail those, and a tough-looking steak turns into something tender enough to eat with a fork and quiet enough to convert skeptics at the table.
FAQ
How long do you broil a London broil in the oven?
For a 1-inch steak, broil 4 minutes per side for rare, 5 for medium-rare, and 6 for medium. Add roughly 1 minute per side for every extra quarter-inch of thickness, and always flip once at the halfway mark.
What temperature do you broil London broil at?
Set the oven to broil, which cycles the top element between roughly 500°F and 550°F depending on the model. Preheat the broiler empty for 5–10 minutes so the element runs at full strength the moment the steak goes in.
Do you need to marinate London broil before broiling?
Marinating for 4–24 hours is strongly recommended because top round and flank are lean and benefit from acid and salt penetration. A dry brine of kosher salt left on the surface for 12–24 hours is a solid alternative when time is tight.
How do you know when London broil is done broiling?
Use an instant-read thermometer inserted into the thickest part from the side. Pull the steak at 125–130°F for medium-rare or 135°F for medium, then account for 5–10°F of carryover rise during the rest.
Should you broil London broil with the door open or closed?
Leave the door cracked about an inch the entire time. A fully closed door traps smoke, can trip the broiler’s thermal sensor, and leaves the cavity too cool for a proper sear.
How do you keep London broil from getting tough when broiling?
Pat the steak dry, pull it 5–10°F below your target temperature, rest it for 7–10 minutes, and slice thin against the grain. Each step shortens the muscle fibers your teeth have to fight through.
