Remove the roast from the marinade. Wipe off excess marinade. Season with Oakridge BBQ Santa Maria Seasoning. Smoke at 250ºF until the internal temperature reaches 110ºF. Remove from the grill. Cover loosely with foil.
If you have a two-piece diffuser, remove the door and place GrillGrates over the firebox. If you have a one piece, completely remove the diffuser plate. Turn the grill up to 475ºF.
When the grill comes up to temp, grill the roast on both sides to achieve nice grill marks. Remove when the internal temperature reaches 125ºF. Rest 10 minutes before slicing thin, against the grain.