Pickled peppers spice up the pork in this sassy stew.
In a large Dutch oven or other heavy pot, heat oil over medium-high. Season pork with salt and pepper and, in batches, brown pork on all sides, about 15 minutes total. With a slotted spoon, transfer pork to a bowl.
Add onion and garlic to pot and cook, stirring often, until onion is softened, about 5 minutes, reducing heat if necessary to prevent burning. Season with salt and pepper. Add 2 cups water, scraping up any browned bits with a wooden spoon. Return pork to pot along with broth, pepperoncini, and oregano. Bring liquid to a rapid simmer and cook until pork is tender, 45 to 50 minutes.
Season with salt and pepper and stir in 1 to 3 tablespoons pepperoncini brine. Discard oregano sprigs and serve over rice.