Rinse the steak under cold running water and pat dry with paper towels. With a sharp knife, make several small cuts in the meat, without cutting all the way through. Press a sliver of garlic into each cut. If you have any garlic left over, set it aside.
In a shallow, non-reactive pan, mix together the olive oil, rosemary, salt, pepper, and any leftover slivers of garlic.
Place the steak in the olive oil marinade and turn to coat. Let sit at room temperature for about 1/2 hour.
Meanwhile, prepare a charcoal fire or preheat a gas grill for direct grilling over high heat. Remove the steaks from the pan, discard the marinade, and place the steaks on the grill. A thicker steak (such as the porterhouse) will take at least 10 minutes per side to reach medium-rare (145 degrees F on an instant-read thermometer) and a thinner steak (such as the T-bone) will take as little as 7 minutes per side.
Remove the steak from the grill and place it on a cutting board. Cover the meat with a piece of aluminum foil to keep it warm, and allow the meat to rest for 5 minutes before slicing it against the grain.
Recipe courtesy of "Al Roker's Big bad Book of Barbeque" Scribners 2002. Copyright 2002 Al Roker