Preheat oven to 350 degrees F., spray or oil a 9 x 13″ casserole
Mix together in a large bowl, the hashbrowns, milk, sour cream, eggs, meat of choice, about 1 1/4 cups Cheddar, 1 1/4 cups White cheese, Ranch seasoning mix, and seasoning salt. Pour into casserole and smooth top.
Cook covered for 1 hour. Remove the cover and gently move the mixture around with a fork, bringing the outside to the center and the center toward the outside (if crunchy edges are your thing, don’t be too thorough around the edges).
Sprinkle with remaining cheese (for most attractive look use large pinches of each alternated around the casserole and extending all the way to the edges) and place back in oven uncovered, for about about 15 minutes until the hashbrown mixture is set and cheese is melted. Allow to sit for 10 minutes before serving.
Garnish with green onion if desired.
Note: This casserole works best with thawed hashbrowns. If no time to thaw, frozen hashbrowns can be spread out in the casserole and baked at 250 degrees F. for 15 to 20 minutes, stirring now and then. They should be slightly cooled before proceeding.