Heat the oil in a skillet over medium-high heat.
Add the onions and sauté for 4 minutes, then stir in the garlic and cook 1 minute.
Stir in the beef and cook until it is browned, then drain some of the fat.
Spoon the mixture into a slow cooker and add the spices.
Cover and cook on low heat for 5 to 6 hours, then spoon into bowls.
Serve with shredded cheddar and diced red onion.