Preheat oven to 350 degrees. Spray 9x13 baking dish with nonstick cooking spray. Take four slices of bread and cut them into 2-inch cubes. Cut the other slices up and put aside. Spread cubed bread into the bottom of the baking dish.
Cover evenly with half of the pastrami and then evenly top with drained sauerkraut
Sprinkle 2 cups of shredded Swiss cheese on top of sauerkraut layer.
Next, top with remaining pastrami. I push down to help compact it a bit.
Whisk together milk, eggs, thousand island dressing and pour mixture evenly over the casserole. Top with remaining cubes bread.
Cover with foil and bake for 45 minutes. After 45 minutes I like to take the cover off and let the bread crisp up.
Remove from oven, let rest for 5 minutes then slice and serve.Enjoy!