Preheat the oven to 375°F. Spray a 9x13-inch baking dish with nonstick spray.
Cook the sausages according to package instructions in the microwave or on the stove. Chop the sausages into 1/2-inch chunks.
In a large bowl, whisk together the eggs, 1 1/2 cups of the cheese, the milk, green onions (reserve about 2 tablespoons for garnish), salt, and pepper. Stir in the sausages.
Pour the egg mixture into the prepared baking dish. Top with the tater tots in a single layer, gently pressing the tots into the egg mixture. Sprinkle with the remaining ½ cup cheese.
Cover and bake the tater tot breakfast casserole for 35-40 minutes, until the eggs are fully set. Remove the cover during the last 10 minutes of baking to brown the top. Remove from the oven and sprinkle with reserved green onions. Let cool in the pan for 10 minutes prior to serving.
Notes
Instead of sausage links, you can use sausage patties and dice them up (or use vegetarian sausage)
MAKE AHEAD: Assemble to the point of baking, refrigerate overnight, then bake as directed.
TO STORE: Place leftover casserole in an airtight storage container in the refrigerator for up to 3 days.
TO REHEAT: Reheat leftover tater tot breakfast casserole covered in a 350 degree F oven or in the microwave.
TO FREEZE: Wrap the casserole in individual portions and freeze for up to 6 months. When ready to bake, let thaw overnight in the refrigerator before reheating according to the instructions above.