Mix together all ingredients in a small bowl
Whisk together vinegar and oil in a small bowl.
Coat both sides of the tri-tip roasts with the seasoning mixture, rubbing it in as you would a dry rub. Let the seasoned tri-tip rest for at least 30 minutes at room temperature.
Sear each side of the tri-tip at 600 to 700 degrees for 3 to 4 minutes each. Remove seared tri-tip from the grill, cover it with foil and let it rest while bringing the temperature down to 350 to 400 degrees.
Put tri-tip back on the grill and and cook to an internal temperature of 126 degrees for medium rare, basting with the sauce every 5 to 10 minutes.
Remove tri-tip, cover it with foil and let it rest 15 minutes. Cut into ½” slices against the grain.