1/3 c. balsamic vinegar
5 garlic cloves, minced
1/3 c. plus 1/4 cup olive oil, plus more for the pans
4 tsp. dried oregano
2 tsp. kosher salt, plus more to taste
1 1/2 tsp. black pepper
2 pork tenderloins (each slightly over 1 pound)
6 sweet potatoes, each cut into 6 wedges
6 shallots, quartered
Chopped fresh parsley, for topping
Whisk the balsamic vinegar, garlic, 1/3 cup olive oil, 2 teaspoons oregano and 1 teaspoon each salt and pepper in a small bowl.
Place the pork in a large resealable plastic bag and pour in the marinade. Seal the bag, place in a dish and marinate for 30 minutes at room temperature or 2 hours in the refrigerator.
Position racks in the upper and lower thirds of the oven and preheat to 450˚. Toss the sweet potatoes and shallots with the remaining ¼ cup olive oil, 1 teaspoon salt, 2 teaspoons oregano and ½ teaspoon pepper in a large bowl.
Lightly oil 2 sheet pans. Put a pork tenderloin on each pan (let some of the marinade drip off first) and season lightly with salt. Arrange the sweet potatoes and shallots cut-sides down around each tenderloin.
Roast, rotating the pans halfway through and shaking them to loosen the potatoes, until a thermometer inserted into the thickest part of the meat registers 140˚ to 145˚ and the potatoes are tender, 20 to 30 minutes. Slice the pork and serve with the vegetables. Top with parsley.