Preheat oven to 375°F and spray a 9x13-inch baking dish with cooking spray.
In a large bowl, combine shredded chicken, frozen vegetables, cream of chicken soup, chicken broth, sour cream, garlic powder, thyme, and black pepper, stirring until well mixed.
Pour the chicken mixture into the prepared baking dish and spread evenly.
Separate the biscuit dough and tear each biscuit into 4 pieces, then scatter the pieces evenly over the top of the chicken mixture.
Bake uncovered for 30-35 minutes until the biscuits are golden brown and cooked through, and the filling is hot and bubbly.
Let stand for 5 minutes before serving.