Preheat your oven to 350°F and prepare a 13x9-inch baking dish by greasing or spraying it with nonstick spray.
In a large mixing bowl, combine the cooked penne pasta, shredded chicken, Alfredo pasta sauce, and ranch dressing. Mix until all ingredients are thoroughly incorporated.
Transfer the pasta mixture to the prepared baking dish, spreading it out evenly.
Evenly distribute the chopped bacon over the top of the casserole, followed by an even layer of shredded mozzarella cheese.
Place the dish in the oven and bake for 15 to 20 minutes, or until the casserole is hot and bubbling. Allow it to rest for 5 minutes before serving. Garnish with chopped parsley if desired.