Prep the oven + pan: Preheat oven to 350ºF (177ºC). Spray a 9×13-inch baking dish with nonstick cooking spray.
Cook the sausage: In a large skillet, cook 2 (9-oz) packages breakfast sausage links until cooked through. Transfer to a paper towel–lined plate, drain off any grease, then slice into ½-inch pieces.
Cook the bacon: In the same skillet, cook 1 pound bacon until browned and crispy. Drain on paper towels and crumble.
Layer the tater tots: Arrange the frozen 32-ounce package of tater tots in a single, even layer in the prepared baking dish
Mix the eggs: In a large bowl, whisk together 12 eggs, ½ cup milk, ¼ cup sliced green onions, ½ tsp salt, and ¼ tsp black pepper.
Add the meats: Stir in the cooked sausage and half of the crumbled bacon.
Cheese layer #1 (in the eggs): Fold in 1 cup Monterey Jack and 1 cup cheddar (this is the first cheese layer).
Assemble: Pour the egg mixture evenly over the tater tots.
Bake: Bake 40–45 minutes, until the eggs are set in the center.
Cheese layer #2 (on top): Sprinkle the remaining 1 cup cheddar evenly over the top. Return to the oven for 5–7 minutes, just until the cheese melts.
Rest + finish: Let stand 10 minutes. Sprinkle with the remaining bacon and 2 Tbsp sliced green onions, then slice and serve.