London Broil Sandwiches: Juicy Steak, Sharp Sauce

London broil sandwiches pair thin slices of marinated, broiled beef with soft rolls, sweet onions, and a tangy horseradish sauce. London broil describes a cooking method rather than one specific cut, so top round or flank steak both work; slicing the cooked meat across the grain keeps each bite tender.

Ingredients

1½ lb (680 g) top round or flank steak, about 1–1¼ in (2.5–3 cm) thick
2 tbsp (30 ml) olive oil
2 tbsp (30 ml) soy sauce
1 tbsp (15 ml) Worcestershire sauce
1 tbsp (15 ml) red wine vinegar
2 garlic cloves (6 g), finely grated or minced
1 tsp (5 g) Dijon mustard
½ tsp (1 g) freshly ground black pepper
½ tsp (3 g) kosher salt, plus more to season the onions if needed
2 medium yellow onions (about 300 g), thinly sliced
1 tbsp (15 ml) olive oil, for the onions
½ cup (120 g) mayonnaise
1 tbsp (15 g) prepared horseradish, or more to taste
1 tsp (5 ml) lemon juice
1 tsp (5 g) Dijon mustard, for the sauce
4 sturdy sandwich rolls (about 280 g total), such as hoagie rolls
4 slices (about 80 g) provolone cheese
1 cup (20 g) arugula or baby spinach

Instructions

Marinate the steak. In a shallow dish or a food-safe resealable bag, mix 2 tablespoons olive oil, the soy sauce, Worcestershire, red wine vinegar, garlic, 1 teaspoon Dijon, pepper, and ½ teaspoon salt. Add the steak and turn it to coat. Cover or seal and refrigerate for 1 hour. For more even seasoning, turn the steak once about halfway through. Do not leave raw beef marinating on the counter.
Prepare the onions and sauce. While the steak marinates, slice the onions and stir together the mayonnaise, horseradish, lemon juice, and the second teaspoon of Dijon in a small bowl. Taste the sauce and add a little more horseradish if you prefer a stronger bite. Cover and refrigerate it until serving.
Cook the onions. Heat 1 tablespoon olive oil in a wide skillet over medium-low heat. Add the sliced onions and cook for 15–18 minutes, stirring every few minutes, until soft and golden. Lower the heat if the edges brown quickly; the goal is tender, sweet onions, not charred ones. Taste and add a pinch of salt if needed. Keep warm while you cook the steak.
Heat the broiler and prepare the beef. Set an oven rack about 4–6 inches (10–15 cm) from the broiler element and preheat the broiler on high. Remove the steak from the marinade and let excess liquid drip off. Discard the marinade because it has touched raw meat. Pat the steak dry so it browns rather than steams, and place it on a broiler-safe rack set over a rimmed pan. If your pan instructions do not allow a rack, use the pan directly and watch for splattering.
Broil to a safe temperature. Broil the steak for about 4–6 minutes per side, turning once; thickness and broiler strength affect the timing. Check the thickest part with an instant-read food thermometer. USDA FSIS sets 145°F (63°C), followed by a 3-minute rest, as the safe minimum internal temperature for whole cuts of beef. If the steak has not reached that temperature, continue broiling in short intervals and check again. Let it rest on a cutting board for 10 minutes before slicing.
Toast the rolls and slice the steak. During the steak’s rest, split the rolls and toast them cut-side up under the broiler for 1–2 minutes, watching closely so they do not burn. If you want warm, melted cheese, put a slice of provolone on each roll and return them to the broiler briefly. Find the direction of the steak’s muscle fibers, then slice thinly across them. If the grain changes direction, turn the steak as you cut so each slice crosses the fibers.
Assemble and serve. Spread horseradish sauce on the cut sides of the rolls. Add arugula, a generous layer of sliced steak, and the warm onions. Close the sandwiches and serve promptly, with extra sauce on the side. For easier eating, cut each sandwich in half with a sharp serrated knife.

Tips

Use the thermometer, not the clock, to judge doneness. A thin flank steak can cook faster than a thick top round, and broilers vary widely. Insert the thermometer from the side into the thickest part of the steak for a reliable reading. The required rest after reaching 145°F (63°C) is part of the safe cooking guidance, not a reason to skip the temperature check.
Make slicing easier. Resting lets the juices settle and gives you time to toast the rolls. Slice against the grain as thinly as you can; thick slices cut with the grain tend to feel chewy, especially with lean top round. A sharp knife and a steady cutting board help you get neat slices without pressing down on the meat.
Adjust the marinade thoughtfully. Soy sauce and Worcestershire both add salt, so taste the cooked onions before seasoning them further. Low-sodium soy sauce is an easy substitute if you want more control. If you do not have red wine vinegar, use an equal amount of apple cider vinegar; it gives a slightly fruitier tang without changing the method.
Choose a useful horseradish substitute. Prepared horseradish gives the sauce its sharp, savory heat. If it is unavailable, use a small amount of wasabi paste or a little extra Dijon, adding it gradually; either substitute changes the flavor, and Dijon will be milder. Avoid adding a large amount at once, since prepared horseradish can vary in strength.

Serving Suggestions

These sandwiches are substantial enough to serve as a main course, but a crisp or acidic side balances the richness of the beef and mayonnaise-based sauce. Try a green salad with a simple vinaigrette, vinegar-dressed slaw, dill pickles, or sliced tomatoes. For a classic casual meal, serve them with oven-baked fries or potato wedges; keep the portions modest if the rolls are large.

For a group, set out the sliced steak, onions, rolls, greens, cheese, and sauce separately so everyone can build a sandwich. Keep the warm ingredients covered while serving, and avoid leaving cooked beef at room temperature for more than 2 hours. If the meal is outdoors in temperatures above 90°F (32°C), refrigerate perishable food within 1 hour. Extra sauce can also be offered as a dip for the sandwich edges.

Variations

Make it without cheese: Skip the provolone and add extra arugula, thinly sliced tomato, or pickled red onion. The sandwich will taste brighter and less rich. For a melty version, Swiss cheese or mild cheddar can replace provolone, though stronger cheeses will stand out more against the horseradish sauce.

Change the sauce: Replace the mayonnaise with thick Greek-style yogurt for a tangier, less rich sauce, or mix mayonnaise with a little sour cream. Keep the horseradish and lemon, then adjust the seasoning after mixing. For a milder sandwich, use only a teaspoon of horseradish and offer more at the table.

Add a smoky note: Use a pinch of smoked paprika in the marinade or add roasted red peppers to the assembled sandwich. These additions bring a different kind of savoriness without requiring a change to the broiling time. Avoid piling on too many wet toppings, which can soften the bread before the sandwich is eaten.

Use another steak cut: Flank steak is a convenient choice, while top round is often leaner and benefits from especially thin slicing. A flat iron steak can also work if it fits your broiler pan, but its thickness may differ, so use the thermometer rather than copying the timing exactly. London broil is not a separate cut of beef, and cuts sold under that name can vary.

Storage and Reheating

For best texture, store the steak, onions, sauce, greens, and rolls separately. Refrigerate cooked steak and onions within 2 hours, in shallow, covered containers; they keep for 3–4 days in the refrigerator. Keep the sauce covered and chilled, and use it within 3–4 days as well, or follow the shorter date on any ingredient package. Discard food that has been left out beyond the safe time rather than relying on smell or appearance.

Reheat only the amount of steak and onions you plan to eat. Put them in a covered skillet with a spoonful of water or broth and warm gently, stirring once or twice, until leftovers reach 165°F (74°C), checked with a food thermometer. This is the USDA FSIS reheating temperature for leftovers. The steak may cook further and become less pink, but gentle heat and a little added moisture help limit drying. Toast fresh rolls separately, then assemble with cold sauce and greens. Freezing cooked steak is possible for up to about 2–3 months for best quality; thaw it in the refrigerator before reheating, and expect the texture to be a little less juicy.

Frequently Asked Questions

What cut of beef is best for London broil sandwiches?
Top round and flank steak are both good options. Top round is lean and widely available; flank steak has a more pronounced grain that is easy to spot when slicing. Since “London broil” usually refers to a preparation rather than a guaranteed cut, check the package and adjust broiling time to the steak’s thickness.

Can I marinate the steak overnight?
You can marinate it for several hours, but this recipe is designed around a 1-hour refrigerated marinade. For an overnight marinade, keep it covered in the refrigerator and avoid extending the time beyond about 12 hours: the vinegar and salt can make the surface overly firm or salty if left much longer. Always discard marinade that has contacted raw beef.

Can I cook the steak in a pan instead of under the broiler?
Yes. Use a heavy skillet that can hold the steak without crowding, and sear it over medium-high heat, turning as needed, until the thickest part reaches 145°F (63°C). The exact time depends on the pan, cut, and thickness. Rest it for 3 minutes after it reaches the USDA FSIS safe minimum, then slice across the grain.

How do I keep the sandwiches from getting soggy?
Toast the cut sides of the rolls, spread sauce in a thin layer, and add the greens between the bread and wetter toppings when practical. Assemble close to serving time rather than storing completed sandwiches. If packing them for lunch, keep the components separate and build the sandwich shortly before eating.

Can I make parts of this recipe ahead?
Yes. Mix the sauce and slice the onions a day ahead, storing each covered in the refrigerator. You can also cook the onions ahead and rewarm them gently. For the best texture, broil and rest the steak shortly before serving; if you cook it in advance, chill it promptly and reheat portions to 165°F (74°C) before assembling.

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Safety notes: safe minimum internal temperatures from USDA FSIS; raw and undercooked fish guidance from the U.S. FDA. Food safety notes

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