Preheat oven to 350 degrees F. Lightly coat a 9 x 13 baking dish with cooking spray and set aside.

In a skillet over medium-high heat, cook the breakfast sausage until brown, crumbling the meat as you go. Once browned, add the chopped red bell pepper and cook for 1-2 minutes until softened. Remove from heat and add shredded potatoes. Place sausage mixture in the prepared 9 x 13 dish, spreading evenly. Spread shredded cheddar cheese over the sausage.

In a medium bowl, whisk eggs. Add milk, black pepper, salt, ground mustard, and paprika and combine. Pour egg mixture evenly over sausage mixture.

Bake for 40-45 minutes, or until a knife inserted in center comes out clean. Remove from oven and allow to cool for 5-10 minutes before serving. Serve with green onion on top if desired.