Spray the inside of your slow cooker with non-stick cooking spray.
Add the shredded chicken, cream cheese cubes, sour cream, ranch dressing, and ranch seasoning mix to the slow cooker and stir to combine.
Sprinkle the cheddar and mozzarella cheese over the top and mix everything together until well incorporated.
Cover and cook on LOW for 2-3 hours, stirring occasionally, until the cheese is completely melted and the dip is hot and bubbly.
Top with crumbled bacon and sliced green onions before serving.
Keep the slow cooker on the warm setting during the party and serve with tortilla chips or toasted bread.