Combine flour, salt and pepper in a shallow dish or large plastic bag. Add pork and toss to coat.
Heat oil in a 3 to 4-quart Dutch oven or heavy-bottomed saucepan over medium-high heat. When oil shimmers, add half of pork (be sure to shake off excess flour before adding) and cook until brown on all sides, about 5 to 7 minutes. Remove to a plate and repeat with remaining meat.
Discard all but about 1 tablespoon of the drippings, return pot to stove, and add onions, peppers, garlic, and oregano. Season with salt and freshly ground black pepper and cook, until golden, about 3 to 5 minutes.
Stir in remaining ingredients and bring to a boil. Reduce heat to low, cover, and let simmer until meat is fork tender, about 1 1/2 hours. Serve.