Brown the beef and turkey with the onions in a large skillet. Drain fat, then transfer cooked meat and onions to a large slow cooker (or stockpot). Add beans, corn, tomatoes, chiles, olives and seasonings; cook in slow cooker on low for 6 to 8 hours (or simmer on low heat for about 1 hour if using a pot on the stove).
To serve: sprinkle a few corn chips in the bottom of a bowl and ladle soup over them. Top with desired garnishes.
Notes
If you are watching your weight, use all lean ground turkey instead of beef and turkey.
Fixings to serve with the soup (like corn chips) are not included in the nutritional information.
This really isn't technically a "soup." It's more like a thick chili-sort of dish and it's fabulous over the corn chips- don't leave those out!
Add sliced, black olives if you'd like (optional).
Consider other garnishes too: guacamole, chopped onions, lettuce, tomatoes, etc.