In a medium skillet, heat oil over medium heat. Cook onions until soft.
Combine all ingredients in a 5qt to 6qt slow cooker and stir well. Cover and cook on Low for 6 - 8 hours.
If it is too thin, let it cook longer with the lid off. The longer it simmers, the better the chili will be.
Alternatively, use 1/4 lb pork sausage for carnivores or 1 whole cup of TVP chunks and omit the beef for vegetarians and vegans.
A note for carnivores: Since my beef is home-ground from extra-lean roasts and used in small quantities, I didn't bother to cook it separately. If you're using a fattier grind, definitely cook it prior to putting it into the cooker to get rid of that fat. It won't be nice in the chili. Smoked sausage would also be excellent in this dish, but I'd definitely brown that first to get as much flavor as possible into the chili.