Combine vinegar and steak seasoning in a medium bowl; stir until seasoning is dissolved. Stir in olive oil until combined.
Place pork into a resealable plastic bag, then pour marinade over pork. Squeeze out air and seal the bag; marinate in the refrigerator for 2 hours to overnight.
When ready to cook, preheat the oven to 350 degrees F (175 degrees C).
Place pork into a glass baking dish along with marinade.
Bake in the preheated oven, basting occasionally, until an instant-read thermometer inserted into the center of the tenderloin reaches an internal temperature of 145 degrees F (65 degrees C), about 1 hour.
Let rest for 10 minutes before slicing and serving.
