Brown the pork sausage in a skillet, breaking into pieces as it cook. Add mushrooms and cook until they are tender and release their moisture. Set aside to cool.
In a large bowl, whisk together eggs, milk, pepper, salt, garlic powder, and onion powder. Add cheese, hash browns, and cooked sausage and mushrooms and mix to combine.
Spray a baking dish with nonstick cooking spray. 8 x 12 or 9 x 13 are great size options.
Pour the egg mixture into the casserole dish.
Bake for 50-55 minutes until the center is set.
Let cool for 10 minutes before serving. Enjoy!
Recipe by For the Love of Gourmet at https://fortheloveofgourmet.com/sausage-mushroom-and-swiss-breakfast-casserole/