Preheat the grill to high heat on one side.
In a small bowl, mix together the olive oil, minced garlic, salt, pepper, thyme, and rosemary.
Pat the steak dry with paper towels, then brush both sides of the steak with the marinade.
Place the steak out of the direct heat on the hot grill with the tenderloin side facing away from the direct heat. Cook for about 5-7 minutes on each side (for medium-rare). The tenderloin side should register 110°F on your meat thermometer.
Now move the steak to direct heat and cook 2-3 minutes on each side, until both sides are seared and the internal temperature reaches 130°F.
Add a tablespoon of butter to the steak during the last minute of grilling for extra flavor and richness.
Once the steak is done, transfer it to a cutting board and let it rest for a few minutes before slicing and serving.