Place the thyme, garlic, oregano, parsley, salt, and pepper in a mortar. Crush well with the pestle to create a paste. Spread the paste on the tenderloins, covering all sides. Cover the tenderloins in plastic wrap and refrigerate for 1 to 4 hours.
Remove the tenderloins from the refrigerator and discard the excess marinade.
Heat a large frying pan on medium-high. Add the oil and brown the tenderloins for 3 minutes on each side.
Place in the oven for 10 to 12 minutes or until a meat thermometer registers 145ºF. The center of the meat should be pink.
Place the tenderloins on a cutting board or level surface and let rest for 10 minutes before slicing.