Fill a pot or sous vide container with water and attach the immersion circulator.
Set the temperature for 131 degrees for medium rare, 140 degrees for medium, or 148 degrees for medium well.
Add salt and pepper to the tenderloin.
Use 1 tablespoon of the olive oil to coat the tenderloin on all sides.
Add rest of the oil, thyme and garlic to the zip lock bag.
Place tenderloin in zip lock bag and squeeze out most of the air.
Once water is up to temperature, slowly lower the zip lock bag with the tenderloin into water allowing any remaining air to escape. Once the air has escaped zip the bag.
Use a binder clip to attach the bag to the side of the pan or to the rack on the container.
Cook for 1.5-4 hours at desired temperature.
Remove the tenderloin from bag, pat dry with paper towel, and lightly salt.
Place on hot grill, searing all sides for 30-45 seconds per side. This will seal in the juices and add a nice char to the tenderloin.
Remove from heat and let rest for 5 minutes.
Carve and enjoy!