It all depends on the thickness of your lamb chops. They will be cooked when they reach an internal temperature of between 125F to 130F (52C to 55C). This will cook them between medium rare and medium. If you want well done chops cook until the internal temperature reaches 135F to 140F (50C to 60C). If you don't have a digital probe thermometer you can use the palm test - - Touch your middle finger lightly with your thumb. Press the fleshy part of your palm below your thumb. If the meat feels like this the meat will be medium rare. - For medium cooked meat, touch your index finger to your thumb, and for well-done meat use your index finger. Just remember, the firmer the meat feels when pressed, the more well-cooked it is.