Heat vegetable oil in a 12-inch skillet over medium heat. Add the flour tortilla. Layer half of the Swiss cheese on half of the tortilla, followed by the corned beef, sauerkraut, and remaining Swiss cheese.
Fold tortilla in half. Cook until golden brown on one side, about 4 to 5 minutes. Flip quesadilla to the other side; cook until golden brown, another 4 to 5 minutes.
Remove from pan; cut into 4 wedges. Serve with Russian dressing on the side. Yield: 2 servings.