Preheat oven to 375°F (190°C).
In a large mixing bowl, stir together the shredded chicken, condensed soup, frozen vegetables, milk, onion powder, and black pepper until well combined.
Transfer the mixture into a 9x13-inch greased baking dish and spread evenly.
Sprinkle shredded cheddar cheese over the chicken mixture.
Arrange the biscuit dough pieces evenly over the top of the casserole.
Bake for 25 to 30 minutes until the biscuits are golden brown and the filling is bubbling.
Remove from oven and let rest for 5 minutes before serving.