The first London broil I grilled looked perfect on the outside and ate like a boot. I trusted the clock, ignored the thermometer, and sliced it too soon. That is how you learn how long to grill london broil for medium rare: use time as a guide, but let internal temperature make the final call. For a 1-inch-thick cut, plan on roughly 8 to 12 minutes total over high heat, turning once. A thicker piece can take 14 to 20 minutes. The difference comes down to thickness, grill temperature, and how cold the beef was when it hit the grate.
Start with the right cut and a hot grill
London broil is a cooking method, not one specific cut of beef. At the grocery store, the label usually means top round steak, though flank steak is also sold for this purpose. Top round is lean and affordable, but it has very little room for overcooking. Medium rare keeps it juicy; medium or well-done can turn it firm and chewy.
Take the beef from the refrigerator 30 to 45 minutes before grilling. Pat it dry, then season it generously with kosher salt, black pepper, garlic, and a little smoked paprika. A marinade with oil, Worcestershire sauce, vinegar, and herbs can help flavor the surface, but it will not magically tenderize the center. For a steak about 1 to 1 1/2 inches thick, use a two-zone fire with one side hot and the other side cooler.
Heat a gas grill to about 450 to 500 F, or build a charcoal fire with a thick layer of hot coals on one side. Clean and oil the grates. If the grates are not hot enough, the meat sticks and cooks slowly enough to lose moisture before it browns. You want a strong sizzle when the beef lands.
How long to grill london broil for medium rare
For a 1-inch-thick top round steak, grill over direct high heat for about 4 to 6 minutes on the first side and 4 to 6 minutes on the second side. That is the practical answer to how long to grill london broil for medium rare, but do not pull it based on minutes alone. Begin checking the thickest part with an instant-read thermometer after about 7 minutes.
Remove the steak at 125 to 130 F for a medium-rare finish. Carryover cooking will usually raise the temperature another 5 degrees while it rests. If you prefer a warmer medium rare, pull it closer to 130 F. Do not poke the thermometer through the side and accidentally read the grill grate or a thin edge. Insert it horizontally into the center of the thickest section.
A 1 1/2-inch steak may need 6 to 8 minutes per side, especially if it starts cold. For a 2-inch roast-style London broil, sear it for 3 to 4 minutes per side, then move it to indirect heat and cover the grill. Cook until the center reaches about 125 F, checking every 5 minutes. This is one of those cases where a clock gives you a neighborhood, not an address.
The grill method that keeps the outside from burning
Put the seasoned beef over the hottest part of the grill and leave the lid closed for the first 3 to 4 minutes. Flip it once the first side has dark grill marks and releases easily. Constant flipping is not a crime, but it makes it harder to build an even crust and track the cooking.
After the second side has cooked for several minutes, check the temperature. If the outside is dark but the center is still below 115 F, slide the steak to the cooler side and finish with indirect heat. This move saved a backyard dinner at my house when Sam bumped the gas knob and pushed the grill hotter than planned. The crust was nearly black, but the middle came out pink instead of gray.
During cooking, avoid pressing the steak with your spatula. That pushes out juices you want to keep in the meat. You also do not need to baste it repeatedly. One light brush of melted butter or reserved marinade near the end is enough. Never reuse marinade that touched raw beef unless you boil it first.
Resting and slicing matter as much as grilling
Once the center reaches 125 to 130 F, move the steak to a cutting board and loosely cover it with foil. Rest it for 8 to 10 minutes. That pause gives the heat time to settle and lets the juices redistribute. Cutting immediately sends flavorful liquid across the board instead of into each slice.
The grain is the direction the muscle fibers run. Find it before slicing, then cut across those fibers at a sharp angle. Aim for slices about 1/4 inch thick. Even a properly grilled steak will seem tough if you cut with the grain. This is the step most people skip after searching how long to grill london broil for medium rare, and it is often the reason dinner still feels chewy.
If the steak rests longer than planned because the kids are finishing homework or the football game goes to halftime, do not panic. A 15-minute rest is fine. Keep it loosely covered, not wrapped tightly, or the crust will soften.
What to do when the timing goes wrong
If the center is under 120 F after resting, return the slices to a hot grill or cast-iron skillet for about 30 to 60 seconds per side. That is better than putting the whole steak back on and overcooking the edges. If the meat reaches 140 F or higher, serve it thinly sliced with a sauce, chopped herbs, or grilled onions. Top round cannot be uncooked, but a sharp cutting technique and a little moisture can still make it a good meal.
If your London broil is dry, the likely causes are simple: the grill ran too hot, the steak was too thin for the timing, or it cooked past medium rare. Next time, start checking earlier and use a thermometer. For a larger cut, indirect heat is safer than trying to blast the whole thing over direct flames.
You can also save leftovers. Chill them within two hours, slice them thin, and use them in steak sandwiches, tacos, or a salad the next day. Reheat gently in a pan with a splash of beef broth rather than microwaving the slices until they curl.
A simple timing plan for Saturday dinner
For dinner at 6:00, season the beef around 4:45 and take it from the refrigerator at 5:15. Preheat the grill by 5:25. Grill a 1-inch steak from about 5:35 to 5:45, checking temperature near the eight-minute mark. Rest it until 5:55, slice across the grain, and get it on the table with potatoes, corn, or a quick green salad.
That schedule answers how long to grill london broil for medium rare without pretending every steak cooks identically. Watch the temperature, protect the rest, and slice thin. Good smoke. Good sweets. Good people.
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