Heat oil in a frying pan. Saute onion for 2 minutes; add ground beef and cook and stir until beef is well done.
Wash and drain kidney beans. Drain some of the juice from the tomatoes.
In a large pot, combine beef, kidney beans, tomatoes, chili powder, salt and oregano. Bring to a boil; reduce and cook slowly for an hour. Stir regularly.
Recipe can be doubled. Freezes well.