If you don't have any A.1., H&P or Worcestershire Sauce you can substitute balsamic vinegar. If you do substitute with the vinegar, shorten the marinade time to no more than 4 hours since the vinegar will start to cook the meat. Do not be afraid if the balsamic discolors the meat during the marinading process. The steak will look normal when you grill/broil it and it will be delicious.