In a large saucepan over medium heat, add the stock, cover and bring to a boil. Then add the orzo and cook, stirring frequently, until al dente, 7 to 8 minutes. Drain the orzo in a colander and allow to cool completely.
In a large bowl, toss together the orzo, chickpeas, tomatoes, feta, olives, vinegar, oil, onion and salt and pepper to taste. Toss in the mint. Serve at room temperature.