Heat olive oil in a large pan over medium heat. Add the onion and garlic. Cook until soft and fragrant.
Add the pearl barley to the pan and toast for 2–3 minutes to bring out a nutty flavor.
Pour in a ladle of warm vegetable broth and stir until it’s absorbed. Continue adding broth one ladle at a time, stirring frequently.
Halfway through cooking (around 15 minutes), add carrots, zucchini, mushrooms, and peas. Keep simmering gently.
Cook until the barley is tender and creamy, about 25–30 minutes total.
Stir in fresh parsley, thyme, salt, pepper, and optional nutritional yeast or vegan parmesan.
Serve warm, garnished with extra parsley if desired.