This salad is easily made a day in advance of serving, through addition of the olives, and stored, covered, in the refrigerator. If making ahead, the flavors of the vinaigrette will really have a chance to soak into the couscous. For best results, return to room temperature and hold arugula, basil, and Feta to add shortly before serving.
Inspired by my Chickpea and Feta Salad
While couscous is cooking, whisk together remaining 5 tablespoons extra virgin olive oil, lemon juice and zest, garlic, shallot, 1/2 teaspoon kosher salt, and 1/2 teaspoon pepper in a large bowl. Add warm, cooked couscous and stir to coat. Stir in chickpeas and tomatoes. Let stand 10 minutes.