1. In a small bowl, mix together garlic, salt, soy sauce, ketchup, vegetable oil, black pepper and oregano.
2. Score both sides of the meat, diamond cut, about 1/8 inch deep. Rub garlic mixture into both sides of the meat. Wrap tightly in aluminum foil, and refrigerate for 5 to 6 hours, or overnight. Flip meat every few hours.
3. Preheat an outdoor grill for high heat, and lightly oil grate.
4. Place meat on the prepared grill. Cook for 3 to 7 minutes per side, or to desired doneness.
My Note: Since the title uses "London Broil" and the recipe uses "Flank Steak" I can see where there would be some confusion. I decided to use London Broil because it was on sale. This is definitely a thicker, tougher cut of meat and needs a longer marinating time 48 hours. I know that seems like a bit much but trust me it will pay off in the end. I used this marinade for 1 & 1/2 pounds of steak. I used kosher salt, low sodium soy sauce, olive oil vs. veg., chili sauce vs. ketchup, and added a splash of white wine vinegar. I put everything into a ziploc bag and let it go, turning it every so often and rubbing the marinade into the meat. After it's grilled to your liking cut against the grain and serve with a baked potato and fresh garden salad!
Now, when London Broils are on sale, I buy several, make a big batch of this marinade, let them sit a day or two, then put them in individual freezer ziploc bags, with the marinade. Then, on a busy day, I can just pull out the pre-marinated steaks, defrost, grill, and enjoy! Great time and money saver, and so yummy!
One time the meat didn't come out very tender so I added about 3 Tbls of lemon juice to act as a tenderizer. I also added about 2 tsp of worchestershire sauce.(we call it rooster sauce), 2 tsp of fish sauce, 1 tsp of ground ginger, chili sauce instead of ketchup and a tsp of garlic powder. I broiled this instead of grilling (due to the nasty weather) and it turned out really good.
Using a london broil vs flank steak (as the recipe indicates) I added 2 tsp of lemon juice to assist in the tenderizing process, then marinated the meat for three days. Definitely more tender than a regular london broil using the marinade -- Next time I'll up the garlic and omit the oregano which overpowered the other flavors in the marinade. Will make again with modifications.