For dry glaze, stir brown sugar, garlic and orange zest to blend.
In a separate bowl, stir remaining ingredients, then add to brown sugar mixture. Set aside until ready to use.
Clean pork tenderloin of any connective tissue. Preheat grill to medium and clean well. Rub tenderloins completely with dry glaze and immediately place on grill.
Grill, uncovered, for about 8 minutes on each side until an internal temperature of 75°C is reached, rotating tenderloins 90° on each side. Let pork sit for a moment before slicing and serving.