Stir together first 3 ingredients.
Rub tenderloin with olive oil, and place on a wire rack in a roasting pan. Pour sherry mixture into roasting pan.
Bake at 450°, basting occasionally, 45 to 50 minutes or until a meat thermometer inserted into thickest portion registers 140° for medium-rare. Bake longer until thermometer registers 160° for medium or 170° for medium-well.
Cover tenderloin loosely with aluminum foil; let stand 15 minutes before slicing. Garnish, if desired. Serve with pan drippings.