Preheat the oven to 375°F (190°C). Spray a 9x13 baking dish with cooking spray and set aside.

Heat the olive oil in a large skillet over medium-high heat. Brown the ground turkey, about 5-7 minutes. Add the chopped onion to the skillet and cook until softened, about 5 minutes. Remove from the heat.

Stir in the cream of mushroom soup, Greek yogurt, half of the shredded cheese, milk, peas and carrots, salt, pepper, and garlic powder until combined. Taste and add additional salt and pepper if desired.

Spread the turkey mixture in the bottom of the prepared casserole dish. Evenly sprinkle the remaining shredded cheddar. Top the cheese with a single layer of tater tots.

Bake the casserole for 40-45 minutes or until the tater tots are crispy and golden brown. Allow the casserole to cool for a few minutes before serving.