Preheat your oven to 375°F (190°C).
In a large mixing bowl, combine the shredded chicken, frozen mixed vegetables, chicken broth, garlic powder, onion powder, thyme, and black pepper. Stir until well mixed.
Pour the chicken mixture into a greased 9x13 inch baking dish.
In another bowl, whisk together the Bisquick baking mix, milk, melted butter, and garlic salt until smooth.
Pour the Bisquick mixture over the chicken and vegetable layer in the baking dish, spreading it evenly.
Sprinkle the shredded cheddar cheese on top of the Bisquick layer.
Bake in the preheated oven for 30-35 minutes or until the top is golden brown and a toothpick inserted in the center comes out clean.
Let it cool for 5-10 minutes before serving.