Combine barley and broth in a large saucepan. Set pain over high heat and bring to a boil. Reduce heat to low, cover, and cook 45 minutes, until barley is tender.
Drain any excess water and transfer barley to a large bowl. Add lemon juice, olive oil, and oregano. Toss to combine. Add vegetables and parsley; toss again. Season to taste with salt and pepper. Serve warm or chilled.