1/2cupyellow onions, diced (or 6 green onions, chopped)
2to 3 cups shredded cheese, mixture of cheddar and mozzarella preferred
More salt and pepper to season the hashbrown layers, to taste
Lightly grease the insert to a large (6 quart) slow cooker with nonstick spray. Layer 1/3 of the hashbrowns on the bottom, then lightly sprinkle with salt and pepper. Top with 1/3 of the cooked sausage, then 1/3 of each the onions and cheese. Repeat layers two more times, ending with the cheese.
In a medium bowl, whisk together the eggs, milk and seasonings. Pour over the layers in the slow cooker. Cook on low for 6 to 8 hours or high for 3-4 hours. (Edges may brown.)