HAHA! I finally get to disagree with Susan. I knew there'd be a day.
Love London Broil. Yep. Can very easily be grilled. Can be melt in your mouth, but it does need to be sliced thin. ((I was thinking; I've never had a tough LB!! Reading SH's response... but it's only 1/2 a disagreement. Because to serve, one slices it at 1/4inch or less.))
London Broil itself can be made of 2 cuts of meat; top round and bottom round. I tend to prefer bottom round, but the it can come from either.
To grill:
I make up a garlic herb paste (several cloves of garlish pressed through a presser or minced very finely), an equal amount of olive oil, and a big fat pinch of dried thyme or any favorite herb blend. Stir them all together. Generously salt the meat on both sides (I prefer sea salt or kosher salt, salt NOT generously if all you have is iodized table salt). Using your hands, smear the garlic herb olive oil paste all over the meat. Wrap in plastic (or cover, or drop in a ziplock bag) and let it sit for an hour or 5 as you do other things.
1) When you're ready to grill, get it going hot hot hot with the grate on.
2) Sear all sides of the london broil. About 5-30 seconds a side. Including ends, small sides, etc.
3) Remove LB to top rack or off to one side for ***indirect heat*** & close lid
4) Flip after 6-10 minutes
5) Bring a sliver of garlic and your meat thermometer out. Poke in legnthwise every 10 minutes (fill hole with garlic sliver so you don't lose juice)
PULL AT
120-25 for rare (hot center, red to pink)
130-35 for medrare (rose pink center)
140-45 for medwell (some red/pink juice, bare hint of pink)
155 for well done (clear juices, no pink)
Once you reach your desired temp, pull it and let it sit for at LEAST 10 minutes. The internal temp will continue to climb. Your 125 will come up to 135 for rare, 150-55 will come up to 165 for welldone, etc. The temp climbs, and then it cools, trapping the juices inside instead of ripping though the muscles and bursting the cells from the escaping steam). So that when you cut into it (1/4 inch slices or less) it will be very very juicy.
One of my fav things to serve alongside is rosemary roasted potatoes. Just quarter red potatoes, place in homemade foil pouch (or storebought pouch or foil container), drizzle over with olive oil, sprinkle with rosemary, seal pouch and cook in indirect heat over the grill. Some corn (just leave in the husk, and dehusk AFTER it's cooled enough to touch, comes off in 2 pulls, including silks), or some grilled peppers or other veggies/ shrooms.
Voila. Outisde dinner.
((Most of your garlic and herb coating will be gone. More than half will be gone after searing it, most will be 'gone' after flipping/cooking. Don't worry. The flavors will have infused from the steam when you're searing it, and little bits got rubbed into the meat and seared inside when you rubbed it in the beginning))