Preheat the oven to 350°F (175°C). Grease a 9x13 inch baking dish.
Mix shredded chicken, sour cream, mayonnaise, cream of chicken soup, cheeses, garlic powder, onion powder, oregano, salt, and pepper in a large bowl until well combined.
Transfer the chicken mixture to the prepared baking dish, spreading it evenly.
Mix crushed crackers with melted butter and sprinkle over the chicken layer.
Bake for 40 minutes or until bubbly and golden brown. Let rest a few minutes, garnish with parsley, and serve.
Notes
Let the casserole rest for a few minutes before serving to allow it to set properly.