Preheat the oven to 350°F (175°C). Grease a 9x13-inch baking dish with cooking spray or butter.

In a skillet over medium heat, cook the crumbled sausage until browned and cooked through, about 5-7 minutes. Add the diced onion and bell pepper, cooking until softened, about 3-4 minutes. Drain any excess fat.

In a large bowl, combine the cooked sausage mixture with the frozen hash browns and half of the shredded cheddar cheese. Mix well.

In another bowl, whisk together the eggs, milk, garlic powder, salt, black pepper, and paprika until fully combined.

Pour the egg mixture over the hash brown and sausage mixture in the baking dish. Stir gently to combine.

Top with the remaining cheddar cheese.

Bake in the preheated oven for 45-50 minutes, or until the casserole is set and the top is golden brown.

Let cool for 5-10 minutes before slicing. Garnish with chopped green onions if desired.