Preheat oven to 400°F and lightly spray an 8 x 8 baking dish with cooking spray to prevent sticking.
Mix the melted butter, cream of mushroom soup, milk, mayonnaise and seasonings together in a large bowl. Add the chicken and rice and stir to combine.
Spread the mixture evenly into the baking dish and bake for 30-45 minutes or until nice and bubbly.
Video
Notes
Store leftovers covered in the fridge for up to 4 days.Freeze baked or unbaked casserole in a freezer-safe container for up to 6 months.Reheat in a 375°F oven until heated through.