In a large skillet cook bacon over medium-high heat until crisp. Using a slotted spoon, remove bacon from skillet and drain on paper towels; crumble bacon and set aside. Reserve 1 tablespoon of the drippings in the skillet; discard the remaining drippings. Add onions, celery, and sweet pepper to drippings in skillet; cook and stir over medium heat about 5 minutes or just until vegetables are tender. Transfer vegetables to a 4- to 5-quart Dutch oven.
Add the 4 1/2 cups chicken broth and wine to Dutch oven; bring to boiling. Add barley. Return to boiling; reduce heat. Simmer, covered, for 25 minutes. Stir in squash. Cook, covered, about 20 minutes more or until squash and barley are tender, stirring occasionally. Remove from heat. Stir in crumbled bacon, sage, salt, and pepper; mix well. (To serve today, omit Steps 3 and 4 and serve warm.)
Lightly grease a 2 1/2- to 3-quart baking dish; spoon squash mixture into baking dish. Cover with plastic wrap; chill for up to 24 hours.
Preheat oven to 350 degrees F. If chilled, remove plastic wrap. If desired, drizzle dressing with an additional 1/4 cup chicken broth to moisten. Bake, covered, for 45 to 55 minutes or until heated through, stirring once. If desired, top with fresh sage leaves.