Preheat your oven to 375°F (190°C).
In a large mixing bowl, combine the shredded chicken, crumbled bacon, ranch seasoning mix, sour cream, and half of the cheddar and mozzarella cheeses. Mix well until all ingredients are evenly coated.
Spread the chicken mixture evenly in a greased 9x13-inch baking dish.
Arrange the frozen tater tots in a single layer on top of the chicken mixture.
Sprinkle the remaining cheddar and mozzarella cheeses over the tater tots.
Bake in the preheated oven for 30-35 minutes, or until the tater tots are golden brown and crispy, and the cheese is melted and bubbly.
If desired, garnish with sliced green onions before serving.