01 - Preheat oven to 180 degrees Celsius (350 degrees Fahrenheit). Lightly grease a 9x13-inch (23x33 cm) baking dish.
02 - In a large skillet over medium heat, cook the breakfast sausage until thoroughly browned. Break apart the meat with a spoon. Drain any excess rendered fat.
03 - Add the finely chopped onion and diced red bell pepper to the skillet with the cooked sausage. Sauté for 3 to 4 minutes, until the vegetables have softened. Remove the skillet from heat.
04 - In a large mixing bowl, thoroughly whisk together the eggs, milk, salt, black pepper, garlic powder, and paprika until well incorporated.
05 - Evenly spread the thawed hash browns in the bottom of the prepared baking dish. Distribute the sausage and vegetable mixture over the hash browns. Sprinkle half of the shredded cheddar cheese over the sausage mixture.
06 - Pour the prepared egg mixture evenly over all the ingredients in the baking dish. Gently shake or tap the dish to ensure the egg mixture settles throughout.
07 - Sprinkle the remaining shredded cheddar cheese evenly over the top of the casserole.
08 - Bake for 45 to 50 minutes, or until the center is set and the top is golden brown and bubbly.
09 - Allow the casserole to rest for 10 minutes before slicing and serving. Garnish with fresh chives or parsley, if desired.