Put the quinoa and water in a medium sauce pan and bring to a boil over medium heat. Decrease the heat to medium-low, cover, and simmer for 15 to 17 minutes, until all of the liquid is absorbed. Fluff with a fork.
Transfer to a medium bowl. Let cool (see note*). Put the cooled quinoa, chickpeas, parsley, tomatoes, and olives in a large bowl. Put the lemon zest, lemon juice, olive oil, garlic, chili powder, salt, and turmeric in a small bowl and whisk briskly until smooth. Pour the dressing over the quinoa mixture and stir gently to incorporate.
Taste and add more chili powder, salt, and/or olive oil if needed. Cover and refrigerate for 2 hours to let the flavors blend.
Right before serving, split the peppers in half lengthwise and seed them. Scoop the quinoa mixture into the pepper halves. Garnish with parsley, if using.