Whisk olive oil, soy sauce, garlic, mustard, salt, and pepper together in a bowl.
Place pork in a large resealable plastic bag and pour in marinade; squeeze out excess air, and seal the bag. Marinate in the refrigerator at least 1 hour before cooking.
Preheat the oven to 350 degrees F (175 degrees C).
Transfer pork to a baking dish; pour marinade over the pork.
Cook in the preheated oven until pork is slightly pink in the center, about 45 to 60 minutes. An instant-read thermometer inserted into the center should read at least 145 degrees F (63 degrees C).
