Preheat your oven to 350°F (175°C).
Spray a 9×13-inch baking dish with nonstick spray.
Cook the Sausage Mixture:
In a large skillet over medium-high heat, brown the ground breakfast sausage, breaking it up with a spatula as it cooks.
When the sausage is about halfway through browning, add the diced onions and bell peppers. Continue cooking until the sausage is fully browned and the vegetables are soft. Drain any excess grease from the skillet and set the pan aside.
Assemble the Casserole:
Place a single layer of frozen tater tots in the bottom of the prepared baking dish.
Sprinkle half of the shredded cheddar cheese and half of the shredded pepper jack cheese evenly over the tater tots.
In a bowl, whisk together the milk, eggs, kosher salt, and black pepper. Pour this egg mixture over the shredded cheese.
Spoon the sausage mixture evenly over the egg mixture.
Top with any remaining tater tots and sprinkle with the rest of the shredded cheese.
Bake:
Cover the baking dish with aluminum foil and bake in the preheated oven for 30 minutes.
Remove the foil and continue baking for an additional 25 minutes, or until the cheese is melted and the casserole is set and cooked through.
Serve:
Let the casserole stand for 10 minutes before slicing to help it set. Enjoy!!
