Cook the orzo in salted boiling water until al dente then drain and rinse the pasta under cold water.
In a small bowl or jug, whisk together lemon juice, lemon zest, sugar, salt, and pepper. Add the garlic and olive oil, and whisk until smooth and combined.
In a large bowl, toss the orzo with half of the dressing and add the chopped veggies and herbs.
Gently toss everything together until coated and chill for 30 minutes.