Pat rinsed and drained sauerkraut dry with paper towels. In a large bowl stir together the sauerkraut, cheddar cheese, Swiss cheese, corned beef, and mayonnaise. Spread in a 9-inch quiche dish or 1-1/2-quart casserole.
Bake, uncovered, in a 350 degree F oven for 25 minutes or until hot and bubbly. Serve warm. If desired, serve with low-carb tortilla chips. Makes 20 (1/4-cup) servings).