Preheat oven to 350°F and lightly grease a 9x13-inch baking dish.
In a skillet over medium heat, cook sausage until browned. Drain excess grease.
Add onion and bell pepper to the skillet. Cook for 3–4 minutes until softened, then stir in spinach and cook just until wilted.
In a large bowl, whisk together eggs, milk, salt, and pepper. Stir in the sausage mixture and shredded cheese.
Pour everything into the prepared baking dish and top evenly with frozen tater tots.
Bake uncovered for 40–45 minutes, or until the eggs are set and the tater tots are golden and crisp.
Let cool for 10 minutes before slicing and serving.