Preheat the oven to 375°F and spray a 9x13-inch baking dish with nonstick cooking spray.
Cook the penne pasta in boiling water until just shy of al dente, then drain.
Season and cook the chicken until it reaches 165°F, then shred it.
Beat the cream cheese until smooth, then mix in sour cream, condensed soup, whole milk, and ranch seasoning.
Cook bacon until crispy, then crumble it.
Combine pasta, chicken, ranch sauce, and half of the bacon. Mix until coated.
Transfer to baking dish, top with remaining cheddar and mozzarella, then sprinkle with the rest of the bacon.
Cover with foil and bake for 20 minutes, then uncover and bake for an additional 10-15 minutes.
Let rest for 5 minutes before serving, then garnish with green onions.
