Preheat oven to 400℉. Grease a 9x13-inch baking dish.
In a large bowl toss bread cubes with melted butter. Spread half of the cubes into the baking dish.
Layer the following: 4 ounce corned beef (about 1 cup), ½ cup thousand island dressing, sauerkraut, 1 cup Swiss cheese, remaining corned beef. Top with the remaining bread cubes.
Cover with foil and bake 25 minutes. Uncover and spread remaining cheese overtop. Bake an additional 10 minutes or until cheese is melted and casserole is heated through. Top with remaining dressing and chopped pickles when serving.
Notes
Broil casserole for 2 minutes for an extra crisp topping.
Refrigerate Reuben casserole covered for up to 3 days.
Reheat in the microwave or covered with foil in the oven.