HEAT oven to 450ºF. Line 15x10x1-inch baking pan with foil; spray with cooking spray.
COMBINE eggs, hash browns, mayo and cheese. Drop, by scant 1/2 cupfuls, into 6 mounds on baking sheet; press each with back of spatula to form 1/2-inch-thick patty.
BAKE 16 to 20 min. or golden brown, turning over after 10 min. Serve with sour cream.