Preheat oven to 350°F (175°C). Lightly grease a 9x13-inch baking dish.
In a large bowl, stir together the chicken, cream of chicken soup, sour cream, garlic powder, onion powder, salt, pepper, and frozen veggies.
Spread the mixture evenly into the prepared dish.
Sprinkle the shredded cheddar cheese over the top.
Cut the biscuits into quarters and evenly distribute them over the top of the cheese layer.
Brush biscuit tops with melted butter, if using.
Bake uncovered for 35–40 minutes or until biscuits are golden brown and cooked through.
Let rest for 5 minutes before serving (it will be hot!).