Heat oven to 375 degrees. On lightly sprayed, foil-lined rimmed baking pan, separate strips of bacon; lay flat in single layer and gently stretch each strip 1-2 inches.
Bake 10-12 minutes, or until bacon begins to curl and edges just start to crisp, rotating pan halfway through cooking. Remove bacon from pans with spatula while warm, draining briefly on absorbent paper; reserve.
Cut bacon slices in half crosswise and tightly wrap around marshmallows, securing with skewer or roasting stick. Roast marshmallows over open fire until toasty brown on edges, being careful not to burn or ignite marshmallows.
Immediately sandwich roasted marshmallows between two graham crackers with a piece of chocolate.