Preheat the oven to 375°F (190°C) and grease a 9×13 inch baking dish.
In a large mixing bowl, combine the cooked and shredded chicken, tomato sauce, diced green bell pepper, diced red onion, and sliced black olives. Stir well to combine.
Spread the chicken mixture evenly into the prepared baking dish.
Sprinkle the shredded mozzarella cheese and grated Parmesan cheese over the top of the chicken mixture.
In a small bowl, mix together the garlic powder, dried oregano, and dried basil.
Sprinkle the herb mixture over the top of the cheese.
Season with salt and pepper, to taste.
Bake for 20-25 minutes, until the cheese is melted and bubbly.
Let the casserole cool for a few minutes before slicing and serving.
Enjoy your delicious Keto Chicken Pizza Casserole!