In a bowl, combine all of the dry ingredients. Evenly coat each side of the tri-tip with the herb mixture. Wrap it in plastic wrap and refrigerate for at least eight hours.
Preheat a grill and lightly oil the grate. You’ll want to keep one side of the grill a bit cooler than the other. On the hot side of the grill, sear each side of the tri-tip so that it’s evenly caramelized. Transfer it to the cooler side of the grill, and let it cook for 20 minutes or until the center is light pink. Remove the tri-tip from the grill and let rest for three minutes. Slice evenly, at an angle.