Preheat your oven to 375°F (190°C) to ensure even baking.

In a large mixing bowl, combine the cooked chicken, artichoke hearts, and frozen chopped spinach. Stir gently.

Stir in the mayonnaise, sour cream, mozzarella cheese, Parmesan cheese, garlic powder, onion powder, black pepper, and salt until creamy.

Grease a 9x13-inch baking dish with olive oil.

Spread the chicken and vegetable mixture evenly into the prepared baking dish, pressing down slightly.

Mix breadcrumbs with melted butter and sprinkle over the casserole, followed by remaining mozzarella and Parmesan cheese.

Cover the baking dish with aluminum foil and bake for 20 minutes.

Remove the foil and bake for an additional 10-15 minutes until the top is golden brown and bubbly.

Remove from the oven and let it cool slightly before serving.