In a medium saucepan combine the broth, mushrooms, and barley. Bring to boiling; reduce heat. Simmer, covered, for 12 to 15 minutes or until barley is tender. Drain thoroughly.
Cut sweet peppers in half lengthwise; remove seeds and membranes. If desired, precook pepper halves in boiling water for 3 minutes. Drain on paper towels.
In a medium mixing bowl stir together the egg, 1/2 cup of the cheese, the tomato, zucchini, bread crumbs, basil, rosemary, onion salt, and bottled hot pepper sauce. Stir in cooked barley mixture. Place peppers, cut side up, in a 2-quart rectangular baking dish. Spoon barley mixture into the pepper halves.
Bake stuffed peppers, covered, in a 350 degree oven for 20 to 25 minutes or until filling is heated through. Sprinkle remaining cheese over the peppers. Return to oven; bake 2 minutes more. Carefully transfer peppers to a serving platter. If desired, garnish with fresh rosemary and dried red chili peppers. Makes 4 servings.