Firstly, it is important to make sure that you have sprayed the grill with some non-sticky spray. Once done, you can plug it in and wait for the light to go off. Medium steak is usually 9 minutes and a well done steak would probably be 10-12 minutes. It is also important to marinate the steaks before putting on the grill. You can start to grill after giving 6 hours to marinate but you may experience a change in flavor. So it is best recommended that you marinate preferably overnight.
Unfortunately (in my experience), you cannot nicely cook a T-bone steak on a George Foreman grill unless you take out the bone. Otherwise, the bone prevents evenly distributed contact with the surface of a George Foreman (or George Foreman type) grill, Uneven contact with the surface of the grill results in unevenly cooked steak. Some parts can be rare to raw with other parts overcooked and dry. You can best cook your T-bone by some other method. Alternatively, take the bone out of meats for good results when using a George Foreman grill. For more information about how to achieve the best results when George Foreman grilling, or for an alternative way to nicely cook your T-bone steak, see Sources and Related Links further down this page.