How Long to Cook London Broil on Grill: Perfect Timing Guide

Perfectly grilled London broil takes 8-12 minutes total for medium-rare (130-135°F internal temperature) when cooked over high heat (450-500°F) on a preheated grill. The exact time depends on your steak's thickness, grill temperature, and desired doneness level.

Grilling London broil seems straightforward until you end up with tough, overcooked meat that's dry as a bone. As someone who's grilled hundreds of London broil steaks across professional kitchens and backyard barbecues, I've learned that timing is everything - but it's not as simple as setting a timer and walking away.

Understanding London Broil: More Than Just a Cut

London broil isn't actually a specific cut of beef - it's a cooking method originally developed for tougher cuts like top round or flank steak. Today, many grocery stores label these same cuts as "London broil" to indicate they're intended for this marinating and grilling technique. This distinction matters because the actual cut affects cooking time and technique.

According to the USDA Food Safety and Inspection Service, the internal temperature is the most reliable indicator of doneness, not cooking time alone. For safe consumption, beef should reach at least 145°F with a 3-minute rest time, though many prefer London broil at medium-rare (130-135°F) for optimal tenderness.

Pre-Grill Preparation: Setting Yourself Up for Success

Proper preparation makes or breaks your London broil experience. Start by selecting a cut between 1-1.5 inches thick - thinner cuts overcook too quickly, while thicker ones become difficult to cook evenly.

Marinating isn't optional for London broil. A minimum 4-hour marinade (up to 24 hours) with acidic components like vinegar or citrus juice helps tenderize the naturally lean, tough cut. My preferred marinade includes olive oil, soy sauce, Worcestershire sauce, garlic, and fresh herbs. The American Institute for Cancer Research recommends avoiding excessive charring during grilling, so keep sugar content in marinades moderate to prevent flare-ups.

Grill Setup: Creating the Perfect Cooking Environment

Your grill setup directly impacts cooking time and results. For London broil, you need two distinct zones:

• High-heat sear zone (450-500°F) for initial searing
• Cooler zone (300-350°F) for finishing if needed

Clean your grates thoroughly and oil them well to prevent sticking. London broil's relatively lean composition makes it prone to sticking more than fattier cuts. For gas grills, preheat with all burners on high for 15 minutes. For charcoal, wait until coals are covered with gray ash before arranging for two-zone cooking.

Cooking Time Guidelines: Your Customizable Timeline

While the standard guideline is 8-12 minutes total for medium-rare, your actual cooking time depends on several factors. The following table provides a more precise reference based on steak thickness and desired doneness:

Thickness	Medium-Rare (130-135°F)	Medium (140-145°F)	Medium-Well (150°F+)
1 inch	6-8 minutes	8-10 minutes	10-12 minutes
1.25 inches	8-10 minutes	10-12 minutes	12-14 minutes
1.5 inches	10-12 minutes	12-14 minutes	14-16 minutes

These times assume direct grilling over high heat (450-500°F). Remember that grill temperatures can vary significantly based on weather conditions, grill type, and fuel source. Always use an instant-read thermometer for accuracy - guessing leads to disappointment with this lean cut.

Doneness Indicators: Beyond the Timer

Relying solely on cooking time is risky. Instead, use these indicators together:

• Internal temperature (most reliable): 130-135°F for medium-rare
• Touch test: Medium-rare feels like the base of your thumb when touching index finger to thumb
• Visual cues: Light pink center with warm red interior
• Juice appearance: Clear juices, not red

The James Beard Foundation emphasizes that pulling your steak 5°F below target temperature accounts for carryover cooking during resting. London broil continues to cook significantly after removal from the grill due to its density.

Resting and Slicing: The Critical Final Steps

Skipping the resting period is the most common mistake with London broil. Allow your steak to rest for 8-10 minutes (tented loosely with foil) before slicing. This lets juices redistribute throughout the meat rather than pouring out when cut.

When slicing, cut across the grain at a 45-degree angle into 1/4-inch slices. Cutting with the grain creates long, tough muscle fibers that are difficult to chew. Proper slicing transforms even slightly overcooked London broil into tender, enjoyable bites.

Avoiding Common London Broil Grilling Mistakes

Even experienced grillers make these critical errors with London broil:

• Over-marinating: More than 24 hours can make the exterior mushy
• Insufficient preheating: Cold grates cause sticking and uneven cooking
• Flipping too often: Limit to one or two flips for proper sear development
• Cutting too soon: Slicing before proper resting releases all juices
• Ignoring carryover cooking: Not accounting for temperature rise during resting

London broil's leanness means it has less fat to protect it from drying out. Unlike ribeye or brisket, this cut offers little margin for error - being just 2-3 minutes over can transform it from tender to tough.

Adjusting for Different Grill Types

Your specific grill type affects cooking dynamics:

• Gas grills: More consistent temperature control; maintain lid closed for even cooking
• Charcoal grills: Higher radiant heat; may require slightly shorter cooking times
• Smoker grills: Not recommended for traditional London broil preparation
• Indoor grill pans: May require 1-2 minutes less per side due to closer heat proximity

Cold weather significantly impacts outdoor grilling. During winter months, add 15-20% to your estimated cooking time as the grill works harder to maintain temperature.

FAQ: London Broil Grilling Questions Answered

Q: Can I cook London broil on a gas grill at lower temperatures?
A: While possible, lower temperatures (below 400°F) increase cooking time significantly, which can lead to tougher meat as the fibers contract more gradually. High heat creates the necessary sear while keeping interior moisture intact.

Q: How do I prevent London broil from becoming tough?
A: Three keys: don't overcook (pull at 130°F for medium-rare), always rest before slicing, and slice across the grain at a 45-degree angle. Proper marinating for 4-24 hours also significantly improves tenderness.

Q: What's the ideal thickness for grilling London broil?
A: 1-1.5 inches provides the best balance. Thinner cuts (under 1 inch) overcook too quickly, while thicker cuts (over 1.5 inches) become difficult to cook evenly without charring the exterior.

Q: Should I close the grill lid when cooking London broil?
A: Yes, keeping the lid closed creates an oven-like environment that cooks the steak more evenly. Opening the lid frequently causes temperature fluctuations that extend cooking time and can lead to uneven results.