Preheat oven to 450F
Grease a 9x13 inch casserole dish with oil spray
Cut potatoes into one-inch dice
In a large mixing bowl, mix potatoes with ¼ cup ranch dressing. Add salt and pepper to taste
Transfer potatoes to the greased casserole dish
Bake potatoes for 30 minutes, mixing one time through cooking to ensure they all cook evenly.
Meanwhile, mix chicken with ¼ cup ranch dressing and marinate while potatoes cook
When potatoes are done, place chicken on top of potatoes and bake 20 mins more (covered with aluminum foil) or until chicken is done.
Take the casserole dish out of the oven and top chicken and potatoes with crumbled bacon, cheese, and green onions
Bake for 10 more minutes, uncovered until the cheese is melted and bubbly.