Preheat oven to 350°F (175°C). Lightly grease a 9x13 inch baking dish.
Spread cooked chicken evenly in the bottom of the baking dish.
Layer the diced ham on top of the chicken.
Add the Swiss cheese evenly over the ham layer.
In a medium bowl, mix the cream of chicken soup, sour cream, garlic powder, and black pepper. Pour the mixture over the layers in the dish and spread evenly.
Sprinkle the stuffing mix over the top.
Drizzle melted butter over the stuffing mix.
Bake uncovered for 30-35 minutes, until the top is golden brown and bubbly.