Coat a large pot with vegetable oil and set over medium-high heat. Add meat, garlic, chili powder and oregano. Stir frequently with a fork to break meat up, and cook until no pink remains, from 5 to 7 minutes.
Meanwhile, finely chop chipotles and chop pepper and onion. Once meat is cooked, stir in all other ingredients.
Bring to a boil, then reduce heat to medium-low. Cover and simmer, stirring occasionally, until vegetables are tender and flavours have developed, 25 to 40 minutes.
Great served with a dollop of plain low-fat yogourt and chopped chives.