Bring a large saucepan of lightly salted water to a boil. Add edamame beans and cook, covered, over medium heat until tender, three to four minutes. Drain and rinse with cold water.
For the dressing, combine oil, lemon juice, garlic, sugar, salt and pepper in a screw-top jar with a tight-fitting lid. Shake to blend.
Combine cooked couscous, lettuce, tomatoes, cucumber, green onions, olives, mint, parsley and edamame in a large bowl. Just before serving, drizzle the lemon dressing over salad and toss to coat well. Sprinkle each serving with feta.
Per serving: 220 calories, 7 g protein, 17 g fat (5 g saturated fat), 10 g carbohydrates, 3 g fibre, 15 mg cholesterol