Have all ingredients ready. Heat a large griddle or skillet over medium-low heat and a medium skillet over low heat.
Divide the corned beef into 4 equal piles and place one one side of a medium skillet with a splash or two of water. Add the sauerkraut on the other side. Steam gently, turning occasionally, until hot.
*Warming up the corned beef and sauerkraut will help melt the cheese and keep the sandwich from getting soggy.
While the corned beef and sauerkraut are warming up, butter one side of each slice of marble rye bread. Then spread Thousand Island dressing evenly on the other side of the bread. Lay the bread butter side down on the griddle in pairs to toast.
Layer two slices of Swiss cheese and ¼ of the corned beef on one side and ¼ cup of sauerkraut on the other side. Grill until the bread is crisp and golden brown, about 2-3 minutes.
Carefully flip the sauerkraut side onto the corned beef side, pressing down slightly. Cook for an additional minute. Serve hot and crispy!