Preheat your oven to 375°F (190°C). Grease a 9x13 inch baking dish with cooking spray or olive oil.
In a large mixing bowl, combine the thawed shredded hash browns, diced bell peppers, diced onions, diced mushrooms, and diced ham or turkey sausage (if using).
Mix well to combine.
Season the hash brown mixture with garlic powder, onion powder, paprika, salt, and pepper to taste.
Stir until the seasonings are evenly distributed throughout the mixture.
Transfer the seasoned hash brown mixture to the prepared baking dish, spreading it out evenly.
Sprinkle the shredded cheddar cheese evenly over the top of the hash brown mixture.
In a separate mixing bowl, whisk together the eggs and unsweetened almond milk until well combined.
Pour the egg mixture evenly over the hash brown mixture and cheese in the baking dish, ensuring that the eggs cover the entire surface.
Place the baking dish in the preheated oven and bake for 40-45 minutes, or until the eggs are set and the top is golden brown.
Once baked, remove the casserole from the oven and let it cool slightly before slicing into squares or rectangles. Serve warm and enjoy!