To make the marinade, mix all of the ingredients except for the beef in a large mixing bowl. Place the trimmed tri-tips in a plastic container and pour the marinade over. Let stand in the refrigerator for at least 6 hours.
Heat grill to medium temperature.
Place tri-tips on grill at a 45 degree angle to establish grill marks and cook about 35 minutes, or until cooked to desired doneness. Remove the tri-tips from the grill and let rest about 2 to 5 minutes before slicing. Serve with your favorite side dishes.