Preheat oven to 375°F and lightly grease a 9x13-inch baking dish.
Cook pasta until al dente, then drain and set aside.
In a large bowl, mix Alfredo sauce, sour cream, ranch seasoning, bacon, and 1 cup Swiss cheese. Add pasta and chicken, stirring to combine.
Transfer to the baking dish and top with remaining Swiss cheese and bacon bits.
Bake for 25–30 minutes, until cheese is melted and beginning to brown. Garnish with parsley and serve.