Remove stalks and tough stems from Swiss chard. Wash leaves thoroughly, and tear into bite-size pieces.
Place in a Dutch oven (do not add water); cover and cook over medium heat 4 to 6 minutes or until tender. Drain well.
Cook bacon in a large skillet until crisp; drain on paper towels. Crumble and set aside, reserving drippings in skillet.
Add Swiss chard to skillet; cook over medium heat 4 to 5 minutes, stirring occasionally. Transfer to a serving dish. Sprinkle with vinegar and bacon.