Thinly slice chard; coarsely chop leaves. Toss together; set aside.
Cook bacon in a large nonstick skillet over medium-high heat for 3 minutes. Add garlic and onion; cook 2 minutes or until tender, stirring frequently.
Add 1/2 of chard and all of broth to pan. Cover, reduce heat, and simmer 2 minutes or until chard wilts. Repeat procedure with remaining chard.
Simmer, uncovered, 5 minutes or until chard is tender, stirring occasionally. Stir in vinegar, salt, and pepper. Cook until thoroughly heated.