Preheat the oven to 350°F (175°C).
In a large mixing bowl, combine the canned chicken, cooked rice, bell peppers, and onion.
Stir in the sour cream, garlic powder, salt, and pepper until well mixed.
Transfer the mixture into a greased baking dish.
Sprinkle the shredded cheese evenly on top.
Bake in the preheated oven for 20 minutes or until the cheese is bubbly and golden.
Remove from the oven and let it cool for a few minutes.
Garnish with fresh herbs before serving.
Serve warm with a side salad or steamed vegetables.
Enjoy your delicious canned chicken casserole!