In a large saucepan bring water to boiling. Add barley and bouillon granules. Return to boiling; reduce heat. Simmer, covered, for 10 to 12 minutes or until barley is tender. Drain and rinse with cold water. Drain well.
In a large mixing bowl stir together drained barley, cucumber, pepper, green onion, parsley, and mint.
For salad dressing, in a screw-top jar combine oil, lemon juice, sugar, salt, and pepper. Cover and shake well. Pour over barley mixture; toss to coat. Cover; chill in the refrigerator for 4 to 24 hours.
To serve, line a salad bowl with lettuce leaves. Spoon the barley mixture into the bowl. Garnish with fresh mint, if desired. Makes 12 servings.