Crosscut from the forward section of the short loin on a steer's middle back, a T-bone steak contains a strip of the top loin and a chunk of tenderloin, both desired cuts on their own. A T-shaped bone from the lumbar separates the two pieces. The tenderloin filet on the larger porterhouse cut—essentially the same steak but for the size—must be at least 1 1/4 inch at the widest point to qualify for the designation; the rules say a T-bone must have at least 1/2 inch.
The T-bone combines the meaty flavor of a strip steak, often called a New York strip when it's sold on its own, with the signature tenderness of the filet mignon. The premium price reflects its position on the animal, coming from the area along the spine with the least used muscles. T-bones come cut at least 1-inch thick, though it's not unusual to find 1 1/2- to 2-inch-thick steaks
The T-bone is made for grilling. Generous bits of fat keep it moist while the tenderloin heart stays tender and flavorful. The intact bone provides a sturdy handle to grab the steak and flip it without puncturing the meat and losing flavorful juice or sparking a flare-up. Stereotypically, this good-looking steak stars on backyard grills in commercials and is often a favorite of the outdoor chef.