Preheat the oven to 375°F (190°C).

In a large skillet, heat the olive oil over medium heat. Add the shredded chicken, garlic powder, Italian seasoning, salt, and pepper. Stir to combine and heat for about 5 minutes until warmed through.

In a mixing bowl, combine the cooked pasta, marinara sauce, half of the Parmesan cheese, and half of the mozzarella cheese. Mix well.

Add the seasoned chicken to the pasta mixture and mix until everything is evenly distributed.

Pour the casserole mixture into the greased 9x13-inch baking dish. Spread it evenly.

Top the casserole with the remaining mozzarella and Parmesan cheese.

Cover the dish with aluminum foil and bake in the preheated oven for 30 minutes.

Remove the foil and bake for an additional 10 minutes or until the cheese is bubbly and golden brown.

Once done, take it out of the oven and let it cool for a few minutes. Garnish with fresh basil or parsley, if using.

Serve warm and enjoy!