Impossible Breakfast Casserole

I made this breakfast casserole for Life Group & it turned out great!

1 lb. pork sausage
1 small onion
2 1/2 cups frozen hash browns
1 cup shredded Cheddar cheese
1/4 cup chopped green onion
1 3/4 cup milk
1 cup Bisquick
4 eggs
1/4 teaspoon salt
1/8 teaspoon pepper
1/2 cup shredded Cheddar cheese

Brown sausage and onion. Drain and mix with all other ingredients except last cheese. Mix and place in large casserole. Top with cheese. Bake at 400 degrees for 40 minutes.

Source: www.cooks.com