Combine marinade ingredients in measuring cup and stir to combine. Place the pork tenderloin in a plastic, sealable bag. Pour marinade over the tenderloin and seal bag. Marinate overnight in the refrigerator.
Preheat an outdoor grill or preheat oven to 350 degrees F.
Remove pork tenderloin from marinade and pat dry. Brush olive oil onto grill and over meat for extra flavor. Reserve marinade. Grill tenderloin until cooked through, about 30 minutes to 40 minutes over medium heat. Or roast in oven for 35 to 45 minutes. Allow meat to rest about 10 minutes before cutting into 2-inch serving pieces.
While meat is grilling, bring reserved marinade to a boil in a small saucepan, then lower the heat and gently simmer until it is reduced to about 2 tablespoons. Stir occasionally. Drizzle a small amount of marinade over each piece of meat.