Preheat your oven to 375 degrees Fahrenheit and lightly grease your baking dish.
In a large mixing bowl, combine the cooked chicken, cooked rice or pasta, cream of chicken soup, sour cream, shredded cheese, vegetables, garlic powder, onion powder, salt, and pepper. Stir until everything is evenly mixed.
Spread the mixture evenly into the prepared baking dish.
In a small bowl, mix the crushed crackers or breadcrumbs with melted butter, then sprinkle the topping evenly over the casserole.
Bake uncovered for 30 to 35 minutes, or until bubbly and lightly golden on top.
Remove from the oven and let it rest for a few minutes before serving.