Spray a 9x13 baking dish with cooking spray and spread half of a 28oz. bag of frozen Potatoes O'Brien to the dish.
Sauté spinach in a large skillet with olive oil until just wilted, 3-5 minutes. Spread the cooked spinach evenly over the potatoes.
In a mixing bowl, combine the eggs, milk, salt, black pepper, white pepper, garlic powder, scallions and optional crushed red pepper flakes. Whisk together until fully incorporated. Pour the egg mixture over the potato/spinach mixture.
Scatter the feta crumbles over the egg mixture, making sure they are evenly distributed. Bake at 350° for 40 minutes or until the eggs are cooked through. Garnish with chopped chives, hot sauce, or your favorite toppings. Enjoy!