Mix cracker crumbs and butter in a 9 inch pie plate. Press into the bottom and up sides of plate forming pie crust.
Saute onions in 2 T of butter until clear but not brown. Spoon into crust. Mix eggs with milk, salt & pepper and pour over onions. Sprinkle with cheeses.
Bake at 350 degrees for 30 minutes or until firm in the center.