Preheat your oven to 375°F (190°C). Begin by bringing a large pot of salted water to a boil for the pasta.
Add the penne pasta to the boiling water and cook according to package instructions until al dente, usually 9-11 minutes. Drain the pasta and set aside.
In a large mixing bowl, combine the cooked penne, diced chicken, chopped sun-dried tomatoes, halved cherry tomatoes, fresh spinach, and minced garlic. Drizzle the olive oil over the mixture and sprinkle in the dried oregano, dried basil, salt, and pepper. Toss everything gently to ensure the flavors are evenly distributed.
Mix in half of the shredded mozzarella and grated parmesan cheese into the pasta mixture. This will help create a cheesy, flavorful base before baking.
Pour the combined pasta mixture into your baking dish, spreading it out evenly. Top with the remaining mozzarella and parmesan cheeses to create a golden, bubbly crust.
Bake uncovered in the preheated oven for 20-25 minutes, or until the cheese is melted and slightly golden on top. The tomatoes will be soft and the spinach will be perfectly wilted.
Remove from the oven and let it cool for a few minutes before serving. This dish pairs wonderfully with a crisp green salad or steamed vegetables.