Cut the flat iron steak lengthwise to form two equal strips. Place all the above ingredients in a large baking pan, or Ziploc bag. Add the meat to it and place in the refrigerator for an hour or more.
Start the BBQ . When temperature reaches high, add the steaks. Cover and cook for 3 minutes. Turn the steaks and cook the other side for another 3 minutes, or to required doneness.