Spray the inside of the slow cooker with non-stick cooking spray.
Add the chicken in a single layer.
Cover with the chopped onions.
Sprinkle on the onion soup mix and add the condensed French onion soup.
Cover and set slow cooker to low for 8 hours.
30 minutes before you're ready to serve sprinkle on the Swiss cheese. Put the cover back on and continue to cook until the cheese is melted and chicken shreds easily with a fork.
