- Preheat your oven to 350°F. 
- In a large mixing bowl, combine the shredded chicken, chopped spinach, cream cheese, sour cream, half of the cheddar cheese, garlic powder, onion powder, salt, and black pepper. Mix until well combined. 
- Transfer the chicken and spinach mixture into a greased 9x13 inch baking dish. 
- In a separate bowl, mix the breadcrumbs with olive oil and the remaining cheddar cheese. Sprinkle this mixture evenly over the top of the casserole. 
- Bake in the preheated oven for 25-30 minutes, or until the top is golden brown and the casserole is heated through. 
- Let it cool for 5 minutes before serving.