Cook the sausage in a skillet on the stove top and drain grease.
Add the frozen hashbrowns, diced onions, and sausage to the slow cooker and stir together (or use clean hands to toss them together).
In a large bowl add the eggs, milk and seasonings. Whisk together.
Pour the egg mixture evenly over the hashbrowns and sausage.
Sprinkle over the cheese.
Place the lid on the slow cooker. Cook on HIGH for 3.5 hours or on LOW for 6 hours. The cooking time will vary from slow cooker to slow cooker. Check at the end of cooking to see if you breakfast casserole needs more time. Scoop into bowls, and sprinkle with green onions for garnish.
Video
Notes
Keep the lid on the entire cooking time for best results.
This breakfast casserole recipe keeps well in an airtight container and when stored in the fridge. It will last up to 4 days and can also be frozen. Let it defrost completely before reheating in the oven or microwave.
You can add other vegetables such as bell pepper, broccoli or mushrooms.