Preheat the oven to 350°F (175°C).

In a large bowl, combine the drained and shredded canned chicken, cooked rice, cream of mushroom soup, frozen mixed vegetables, garlic powder, and black pepper. Mix well.

Transfer the mixture to a greased casserole dish.

Sprinkle shredded cheddar cheese on top of the mixture.

In a small bowl, mix breadcrumbs with melted butter and sprinkle over the cheese layer.

Bake in the preheated oven for 30 minutes or until bubbly and golden brown.