Best Breakfast Casserole

Preheat oven to 350°F. Lightly coat a 13- x 9-inch baking dish with cooking spray. Heat a large skillet over medium-high. Add sausage, and cook, stirring often to crumble, until browned, about 7 minutes. Transfer to a paper towel-lined plate. Do not wipe skillet clean.

Add bell pepper to skillet, and cook over medium, stirring often, until tender, 3 to 4 minutes. Transfer to plate with sausage.

Whisk together eggs, half-and-half, onion powder, 1 teaspoon of the garlic salt, and 1/2 teaspoon of the black pepper in a bowl until fully combined; stir in sausage, bell pepper, Cheddar cheese, and pepper Jack cheese.

Toss hashbrowns with remaining 1 teaspoon garlic salt and 1/2 teaspoon black pepper in prepared baking dish; spread in an even layer. Pour egg mixture over hashbrowns. Press to fully submerge hash browns in an even layer.

Bake in preheated oven until eggs are set in center and hash browns are golden brown, about 45 minutes. Let stand 15 to 20 minutes before serving. Sprinkle with scallions.