Preheat oven to 350°F; spray a 9x13-inch dish with cooking spray.
Cook sausage in a large skillet over medium 7-8 minutes, breaking it up, until browned and fully cooked; drain excess grease.
Spread sausage evenly in dish; sprinkle with 1 cup cheddar.
Arrange frozen tots in a single layer over cheese and sausage; slight crowding is fine.
Whisk eggs, milk, salt, pepper, and garlic powder in a large bowl; pour evenly over tots.
Bake uncovered 40 minutes; top with remaining 1 cup cheese and bake another 5 minutes until melted and bubbly.
Cool 5 minutes before serving so eggs set for clean slices.