Spray a large skillet and heat it over medium-high heat. Add the beef and saute breaking it up with a spoon or spatula into crumbles, until it is browned throughout. Drain in a colander.
Carefully wipe out the skillet and return to medium heat. Add the oil, and then add the onion and bell pepper and saute for 4 minutes until the vegetables have started to soften. Add the garlic and cook for another minute until you can smell the garlic. Add the tomato paste, chili powder, cumin and oregano, stir to combine, and then turn the mixture into a slow cooker. Add the browned beef, kidney beans, tomatoes, cayenne and salt and pepper and stir well. Cook on low for 8 hours.