You might argue that T-bone steaks don't need tenderizing and you could be right, certainly where the fillet is concerned. But the sirloin can often use a bit of help and, anyway, my recipe does add some flavor.
Marinades are a matter of choice and what I give below is only a suggestion, but it comes with good provenance. It's Greek in origin and you would pay a lot of money to have this cooked for you in Iraklion.
You need:
4 T-bone steaks
1 glass white Retsina or other Greek white wine
1 bunch chopped oregano
3tbs good olive oil
2 cloves garlic, finely chopped but not crushed
juice of a lemon (about 60ml)
Combine all the ingredients except the steak in a bowl and whisk lightly. Put the steaks in a food-proof bag such as an oven roasting bag and add the marinade. Turn several times to thoroughly coat the steaks and leave in the refrigerator for at least four hours and preferably overnight, turning from time to time.
Fire up the barbecue and let it get hot. Drain the steaks and discard the marinade. Rapidly cook the steaks on the barbecue grill for 2 minutes a side and allow to stand for two minutes before serving.