Preheat your oven to 400°F (200°C).
Shred your cooked chicken into bite-sized pieces.
In a large mixing bowl, combine the shredded chicken with the ranch seasoning mix.
Add the sour cream, shredded cheddar cheese, and frozen mixed vegetables to the bowl. Stir until well combined.
Grease a 9x13-inch baking dish and spread the chicken mixture evenly across the bottom. Arrange the frozen tater tots in a single layer on top.
Drizzle the olive oil over the tater tots, and sprinkle with garlic powder, salt, and pepper. Bake for 30-35 minutes until golden brown and crispy.