Preheat your oven to 350 degrees F.
Squeeze excess liquid from sauerkraut and place it into a large bowl and combine with softened cream cheese, sour cream, dressing, chopped corned beef (or pastrami), gruyere, garlic powder and black pepper.
Transfer the mixture to a 9 X 9 casserole dish, even out with a spatula.
Place into the oven and bake for 25-30 minutes, or until it starts to bubble around the edges and hot and melted all the way through.
Remove from the oven, and let dip rest for 10 minutes. Garnish with chopped parsley and serve with toasted rye bread crackers or chopped carrots and celery.
Store leftover dip in an airtight container in the refrigerator for up to 4 days. Reheat in the microwave or enjoy cold.