Beef tenderloin is often cooked as a whole roast. Cooking times vary, depending on the size of the tenderloin. Many recipes involving beef tenderloin call for a 2 1/2 to 3 lb. cut. Beef tenderloins retain their shape when tied with kitchen string. If you're unsure how to tie the tenderloin yourself, a butcher can do it for you. Have a meat thermometer handy, as using a meat thermometer is better than relying on a timer alone if you want an accurate temperature reading.
Preheat your oven to 425 F. Prep the tenderloin according to your favorite recipe. Many recipes involve rubbing the tenderloin with olive oil and seasoning it before cooking.
Place the tenderloin on a roasting pan. Roast the tenderloin, uncovered, in a 425 F oven. Turn the tenderloin during the roasting process to ensure it's evenly cooked on both sides.
Insert a meat thermometer into the center of the tenderloin. For a 2 1/2 to 3 lb. tenderloin, a meat thermometer should read 145 F for medium-well. For the same size tenderloin, medium-well should take roughly 40 to 45 minutes.
Remove the beef tenderloin from the oven and let it rest for about 10 minutes before eating.