Mix all ingredients together in a bowl and pour over the tri-tip. Cover and marinate overnight in the refrigerator.
Remove the tri-tip from the refrigerator at least 1 hour before grilling. Wipe off all excess marinade from the meat and place on the spit. Grill the tri-tip for about 1 hour, or until the internal temperature reaches 160 degrees F. Let the tri-tip rest at least 10 minutes before slicing. Enjoy!