In a large pot, heat the oil over medium heat. Add the onions and garlic and fry for 15 minutes, stirring occasionally, until golden brown. Add the carrot and leeks, and stir-fry for 1 minute.
Add the broth, barley, salt and pepper. Bring to a boil, reduce the heat to low, cover and simmer stirring occasionally for 1 hour, or until the barley is tender.