The best way to improve the flavor and keep the outside moist is to poke holes in the tenderloin and add flavorful fillings, such as capers, sun-dried tomatoes, roasted red peppers, even apricots and dried cranberries. This recipe calls for olives.
1. Season the pork all over with salt and pepper. Using a sharp knife, make several slits in it about 1/2 inch deep. Stuff the olievs into the slits. Place the pork in a zip-lock plastic bag.
2. Whisk together the vinegar, oil, brown sugar, mustard, and oregano until the sugar dissolves. Pour the mixture all over the pork and seal the bag. At this point, you can refrigerate the bagged pork for up to 3 days or freeze for up to 3 months.
3. When you're ready to cook it, thaw the pork if necessary. Preheat the oven to 400 degrees F. Coat a roasting pan with cooking spray. Remove the tenderloin from the bag, place it in the pan, and pour the sauce over it. Bake until a thermoter inserted into the thickest part reads at least 160 degrees F, 30 to 40 minutes. Let the pork stand 10 minutes before slicing crosswise into 1-inch thick slices.
From Robin Miller's Quick Fix Meals.