Stir hash browns and 1/2 of the onions together in a 9x13 inch baking dish, then lay cheese slices on top and layer chicken over cheese. In a small bowl, mix soup and milk together and pour mixture over chicken.
Bake in preheated oven for 30 to 35 minutes, or until chicken is cooked through and juices run clear. Pour corn onto chicken and stir to combine all ingredients, then bake for an additional 20 minutes.
Sprinkle remaining onions over all and bake for another 5 minutes, or until onions are golden brown. Let sit 5 minutes before serving.
