Preheat the oven to 375 degrees Fahrenheit. Spray a 9 x 13 x 2-inch baking dish with nonstick cooking spray. Cook 12 ounces uncooked penne pasta according to the package directions, though you can cook it a couple of minutes less than called for if you prefer more al dente pasta. Drain and set aside.
Mix 3 cups shredded cooked chicken breast, half of the 8 slices chopped crispy bacon, 3 cups Alfredo sauce, 1 (1-ounce) packet ranch seasoning, half of the 2 cups shredded mozzarella cheese and half of the ½ cup shredded parmesan cheese. Add salt and ground black pepper to taste.
Add the cooked pasta and stir until evenly combined. Then transfer the mixture into the prepared baking dish. Top evenly with the remaining bacon, mozzarella, and parmesan cheese.
Bake uncovered for 15-20 minutes until the cheese is melted and browning. Remove the casserole from the oven and let it rest for at least 5 minutes before garnishing with chopped fresh parsley and serving.
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Notes
Storage: Store leftovers in an airtight container in the fridge for up to 5 days. Reheat in the oven at 350ºF or microwave in 30-second bursts; freezing isn’t recommended, as the sauce can turn grainy.