Preheat oven to 350°F (175°C). Grease a 9×13-inch baking dish with butter and set aside.
In a large skillet over medium-high heat, cook and crumble the beef breakfast sausage until fully cooked.
Add the frozen tater tots, cooked sausage, and 1½ cups of cheese to the prepared baking dish. Stir to evenly distribute.
In a medium bowl, whisk together the eggs, milk, salt, pepper, garlic powder, and onion powder.
Pour the egg mixture evenly over the tater tot mixture. Sprinkle the remaining ½ cup cheese on top.
Bake uncovered for 55–60 minutes, or until the eggs are set and the top is golden brown.
Let rest for a few minutes before slicing and serving warm. This Tater Tot Breakfast Casserole is best enjoyed fresh.