To achieve the degree of doneness you want, place a meat thermometer deep in the large end of the tenderloin and cook to 5 to 10 degrees below the desired temperature, or use an instant-read thermometer. The temperature for medium rare is 145°F (63°C), for medium 160°F (71°C), and for well done 170°F (77°C). When done, remove the roast and let it stand 15 to 20 minutes before carving. The roast will continue cooking as it stands.
Place the meat on a rack in a shallow roasting pan in a hot oven—425°F (22°C)—and cook until the meat reaches the desired degree of doneness, 50 to 70 minutes.
Brush the tenderloin with oil and place it directly over medium-high heat. Cook, turning occasionally, until the tenderloin roast reaches the desired degree of doneness, 35 to 60 minutes.
Heat oil in a deep skillet and brown the meat on all sides. Add cooking liquid and seasonings if desired, bring to a simmer, and then reduce the heat. Simmer 10 minutes per pound (445g) or until the tenderloin roast reaches the desired degree of doneness.