Cook bacon in a large skillet over medium heat until crispy; reserve ¼ cup for garnish.
Drain excess grease, leaving 2 tablespoons in the pan. Add chicken, onion, salt, and pepper; cook 5–6 minutes until lightly browned.
Stir in ranch seasoning and chicken stock; bring to a boil.
Add uncooked penne, cover, and simmer 15–20 minutes until pasta is tender.
Stir in cream cheese and cream of chicken soup until smooth. Add 1½ cups Colby Jack cheese and cooked bacon; mix until creamy.
Top with remaining cheese, cover 3–4 minutes to melt, and garnish with bacon and parsley.
