Combine all the seasoning ingredients in a bowl. Coat the tri-tip with the rub and place in the refrigerator for 1 hour.
Preheat grill over low heat.
Sear both sides of the beef on the grill, then cook over low heat for about 30 minutes constantly turning or until internal temperature reaches 130 degrees F on an instant-read thermometer. Remove from grill to a cutting board and let rest for 10 minutes. Thinly slice and serve.