Place pork into a resealable plastic bag and pour the balsamic vinegar, olive oil, and steak seasoning on to; make sure to get the ingredients mixed together. Squeeze out any air and seal the bag. Marinate for at least 2 hours or overnight; the longer it marinates, the better it will taste.
Preheat oven or grill to 350 degrees F and line a baking dish with aluminum foil.
Place pork into a glass baking dish along with the marinade. Bake in preheated oven or grill, basting occasionally until the pork reaches an internal temperature of 145 degrees F. This should take about 45-60 minutes. The marinade might start to smell like it's burning in the pan on the sides but the pork is not. Let the roast rest for 10 minutes before slicing and serving to let the juices settle.