Combine broth and porcini in a large saucepan. Bring to a boil; stir in barley. Cover, reduce heat, and simmer 12 minutes or until tender.
While barley cooks, heat oil in a Dutch oven over medium-high heat. Add shiitake, onion, salt, rosemary, and presliced mushrooms; sauté 5 minutes. Stir in Marsala; cook 1 minute. Stir in barley mixture and vinegar; cook 2 minutes or until thoroughly heated, stirring frequently.