Preheat your oven to 375ºF (190ºC) and lightly grease a 9x13-inch (23x33 cm) glass pan with cooking spray.
In a large bowl, combine the cooked chicken, cream of chicken soup, sour cream, cheddar cheese, and frozen mixed vegetables. Mix well.
Open the cans of refrigerated biscuits and cut each biscuit into four pieces. Add the biscuit pieces to the chicken mixture and toss gently until well coated.
Pour the biscuit mixture into the prepared pan, ensuring the biscuits are spread out evenly.
Bake in the preheated oven for 25-30 minutes, or until the biscuits are golden brown and the filling is bubbling.
Remove from the oven and let it cool for a few minutes before serving. Enjoy the warm and comforting Chicken Pot Pie Bubble Up Casserole!