In a large bowl, mix together the brown sugar, salad dressing, pineapple juice, and soy sauce. Pour half of the marinade into a gallon-sized resealable bag and cover the other half of the marinade and place in the fridge until you are ready to grill.
Slice the tenderloins ¾ inch thick and then place tenderloins into the bag and place in the fridge to marinate. You will want to marinate them for at least 30 minutes, but I think that they taste best when they marinate for 4-6 hours.
Grill over medium heat for 4-5 minutes per side or until the internal temperature reads 160℉, basting the entire time with the reserved marinade.
Notes
Be sure to use a hot grill to achieve a nice initial sear, creating crispy pork medallions that trap in moisture to make a delicious pork tenderloin recipe with those tasty browned bits on the outside.
Marinating is key to getting the flavor to penetrate throughout the whole pork loin.
To make an extra crispy coating on the delicious pork medallions, place the marinated pork into a mixing bowl with a little bit of all-purpose flour with some garlic powder before frying to a golden brown perfection.