Spray a square (8x8 or 9x9) baking dish with cooking spray.
Mix all ingredients together in a large mixing bowl.
Transfer the potato mixture to the baking dish spreading it evenly.
Bake for approximately 45 minutes or until cheese is melted and the top of the casserole is nicely browned.
Notes
To store leftovers, cover tightly and keep refrigerated for up to 3 days. Reheat, covered, at 350 degrees for about 20 minutes.
To freeze: I'd suggest portioning the leftovers into servings and then wrapping each serving in plastic wrap. Place the wrapped servings in an airtight freezer container and store for up to 3 months. Thaw in the refrigerator overnight before reheating and serving.