Mix the soup, sour cream, green chilies, chopped onion together in a large bowl and add chicken.
Spread half of this mixture on the bottom of a baking pan. Add cheese to the tortillas and roll them up and lay them on the mixture in the pan. When the pan is full, add the remaining half of the mixture over the top of the tortillas.
Sprinkle with a little bit of cheese and put in oven at 400° until cheese is melted inside tortillas.