Cook potato in a medium saucepan in boiling water to cover 10 to 15 minutes or until tender. Drain well, and let cool.
Combine salsa, red wine vinegar, and oil, stirring mixture well.
To serve, place 1 1/2 cups lettuce and 1/2 cup endive on each of 4 plates. Arrange potato, beef, tomato, cucumber, and onion evenly over lettuce and endive. Spoon salsa mixture evenly over salads.