Bring 1.5 cups of water to a boil in a medium sauce pan. Add the couscous, mix well and turn off the heat. Cover the pot and set aside for 10 minutes, so the couscous has a chance to absorb the water and get tender.
In the meantime, chop all the veggies and toss all the ingredients in a large bowl. If using avocado, add it right before serving.
Finally add the cooked couscous and gently toss to combine. Serve at room temperature or chilled.