- In a large skillet over medium heat, brown the sausage until no longer pink, about 5-7 minutes. Break it up with a wooden spoon as it cooks for even browning. 
- Add the diced onion and bell pepper to the skillet with the cooked sausage. Sauté until softened, about 4-5 minutes. 
- In a large bowl, whisk together eggs, milk, garlic powder, dried thyme, smoked paprika, salt, and pepper until well combined. 
- Grease a 9x13-inch baking dish. Spread the thawed hash browns evenly across the bottom. Layer the sausage and vegetable mixture on top, then sprinkle with 1½ cups of the shredded cheese. 
- Pour the egg mixture evenly over everything. 
- Cover the baking dish with plastic wrap and refrigerate for at least 8 hours or overnight. 
- When ready to bake, preheat your oven to 350°F (175°C). Remove the casserole from the refrigerator while the oven preheats (about 20 minutes) to take the chill off. 
- Bake uncovered for 35 minutes, then sprinkle the remaining ½ cup of cheese on top and bake for an additional 10 minutes until the center is set and the top is golden brown. 
- Let the casserole rest for 5-10 minutes before serving. Garnish with sliced green onions just before bringing it to the table.