Whisk together all ingredients for the marinade in a measuring cup.
Place pork tenderloin in a plastic freezer bag and pour 1/2 of the marinade over top, reserving the second half. Marinate on counter for 20 minutes.
TO GRILL: Heat two burners on grill and place pork tenderloin on, rotating every 2 minutes for 20 minutes total or when internal temperature reads 140 degrees (it will continue to cook when tented with foil). Remove from grill, tent with foil and let rest for 10 minutes before slicing.
TO ROAST: Heat oven to 375 degress. Place pork tenderloin on a sheet pan lined with foil into the oven and roast for 25 minutes or when internal temperature reads 140 degrees (it will continue to cook when tented with foil). Remove from oven, tent with foil and let rest for 10 minutes before slicing.