The exact cooking time for beef tenderloin depends not only on size but also on the temperature of the oven and the desired level of doneness for the meat; for example, at 425 degrees Fahrenheit, a 2-pound beef tenderloin can be cooked for 35 to 40 minutes for medium rare or 45 to 50 minutes for medium. At this same temperature, larger pieces of meat require longer cooking times, and smaller pieces require shorter cooking times. The meat can also be tested for doneness by inserting a meat thermometer into the meat and determining internal temperature; 135 F is a rough minimum internal temperature for a medium-rare beef tenderloin.
Internal temperature can help cooks determine whether their beef tenderloin roast is done even if they choose to cook their meat at a higher or lower temperature than the above-recommended 425 F. Smaller cuts of meat, such as a 1-pound beef tenderloin roast, will be done at a higher temperature than larger cuts. For example, a 1-pound roast will be considered medium rare at 140 F and medium at 155 F. These internal temperature suggestions apply to the meat right when it is removed from the oven. The temperatures should register slightly higher after the meat has had time to rest.