How to Cook London Broil: Tender Steak Every Time

London broil isn't a cut—it's a cooking method for tough steaks like flank or top round. Marinate 4+ hours, then grill or broil 5-7 minutes per side for medium-rare. Rest 10 minutes before slicing thinly against the grain. Skip marination or slice with the grain? You'll get shoe-leather steak. Learned this the hard way after torching my first three attempts.

Wait—What Exactly Is London Broil?

Okay, let's clear this up first because it trips up everyone. London broil isn't a specific cut of beef—it's a technique. Back in the 1930s, butchers started calling top round or flank steak "London broil" to move tougher, cheaper cuts. Today? You'll see it labeled at stores, but it's usually flank steak (thin, grainy) or top round (thicker, leaner). Pro tip: Check the actual cut name on the package. Flank needs more marination; top round handles high heat better.

Always check if you're working with flank (needs aggressive marinating) or top round (more forgiving)

Why Your London Broil Keeps Turning Out Tough

I've seen home cooks panic when their "fancy" steak turns chewy. Truth is? Two rookie mistakes wreck 90% of attempts:

• Skipping the marinade: These cuts have zero marbling. Acid (like vinegar or citrus) breaks down fibers, while oil carries flavor deep. No marinade = cardboard texture.
• Slicing with the grain: See those long muscle fibers? Cut parallel to them, and you're making steak rope. Always slice perpendicular—like cutting across tree rings.

Fun fact: Butchers started this method specifically to tenderize cheap cuts. Respect the process, or pay the price.

Your No-Stress Cooking Guide (Grill or Oven)

Here's the exact method I use after testing 17 variations. Works whether you're grilling or broiling:

1. Marinate 4-12 hours: Mix ¼ cup soy sauce, 2 tbsp olive oil, 2 minced garlic cloves, 1 tbsp Worcestershire, and 1 tsp black pepper. Massage into steak. (Flank needs 8+ hours; top round 4 is fine.)
2. Pat dry + oil: Wipe off excess marinade—wet meat steams instead of searing. Lightly coat with neutral oil.
3. High-heat sear:
   • Grill: 450°F+ direct heat. 5-7 min/side for 1" thick (flip once!)
   • Oven broiler: Rack 6" from heat. 6-8 min/side on preheated cast iron
4. Rest 10 minutes: Tent loosely with foil. This lets juices redistribute—skip it, and you'll bleed flavor onto the cutting board.
5. Slice against the grain: Aim for ¼" strips. Angle your knife 45° for tender bites.

Perfect grill marks mean your surface temp is hot enough—aim for 450°F+

Cooking Method	1" Thick Steak	1.5" Thick Steak	When to Avoid
Charcoal/Gas Grill	5-7 min/side	7-9 min/side	Rainy days or apartment balconies (safety first!)
Oven Broiler	6-8 min/side	9-11 min/side	Thin flank steaks (dries out fast)
Sous Vide + Sear	1-2 hrs @ 130°F + 90-sec sear	2-3 hrs @ 130°F + 90-sec sear	If you don't own the gear (overkill for weeknights)

Three "Expert" Tips That Actually Matter

After 20 years of testing, here's what separates okay from amazing:

• Freeze before slicing: Pop the cooked steak in the freezer 15 minutes. Makes thin slicing way easier—no more jagged edges.
• Acid balance: Too much vinegar? Meat turns mushy. Stick to 2-3 tbsp acid per cup of marinade. Lemon juice > vinegar for subtlety.
• Thickness is king: Anything under ¾" will overcook before you blink. Ask your butcher for 1.25" cuts—or stack two thinner steaks.

When to Ditch London Broil Entirely

Look, it's not magic. Avoid it when:

• You need weeknight speed: Skirt steak cooks in 3 minutes and has better flavor.
• Serving crowds: Brisket or chuck roast feeds more people for less money.
• Rare requests: London broil dries out past medium. Go ribeye if rare is demanded.

But for budget-friendly steak nights? Still my go-to. Just don't expect filet mignon tenderness.

Everything You Need to Know

Q1: Can I cook frozen London broil without thawing?

Nope—never cook frozen. You'll get a charcoal exterior with raw center. Thaw overnight in the fridge. If rushed, submerge sealed bag in cold water for 1-2 hours. Pat dry before marinating.

Q2: Why does my marinade make the steak mushy?

Too much acid or time. Vinegar/lemon >4 hours breaks down proteins excessively. For flank steak, max 12 hours; top round max 8. Use yogurt-based marinades for longer soaks—they tenderize gently.

Q3: How do I store leftovers without drying them out?

Slice immediately after cooking, then store in airtight container with 2 tbsp cooking juices. Reheat gently in skillet with splash of broth—never microwave. Keeps 3 days max; after that, texture turns rubbery.

Q4: Is London broil healthy compared to other steaks?

Yes—it's leaner than ribeye or sirloin. A 4oz serving has 180 calories and 8g fat vs. ribeye's 290 calories/22g fat. But skip sugary marinades; use herbs and citrus for clean flavor.