In a medium saucepan, bring 3 cups of vegetable broth to a boil and stir in barley.
Cover, reduce heat to medium and simmer for 60 minutes or until tender adding up to 1 more cup of broth if needed.
While barley is cooking, heat oil in a pan and sauté garlic, onion, and carrots about 5 minutes. Add zucchini, yellow squash, and thyme and continue to sauté until all vegetables are tender about 5 more minutes.
Remove from heat and keep warm.
When barley is tender, combine barley and sautéed vegetables and season with salt and pepper to taste. Top with parmesan cheese and serve.