Preheat your oven to 400°F. Prepare the chicken and bacon by shredding the chicken and crumbling the bacon.
In a large mixing bowl, combine shredded chicken, crumbled bacon, ranch seasoning mix, and sour cream. Mix until well combined.
Add shredded cheddar cheese to the mixture and stir gently.
Grease a 9x13 inch baking dish and spread the chicken mixture evenly across the bottom. Fold in frozen mixed vegetables.
Layer frozen tater tots on top of the chicken mixture in a single layer.
Bake for 25-30 minutes until tater tots are golden brown. Sprinkle shredded mozzarella cheese on top and bake for an additional 5-10 minutes until melted.
Let the casserole cool for a few minutes before serving. Garnish with chopped green onions if desired.