Add the quinoa and water into a small saucepan. Bring to a boil, then reduce heat to low, cover, and simmer for 15 minutes. Remove the pan from the heat and leave covered for 5 minutes. Remove the lid and fluff the quinoa with a fork. Set aside to cool for another 15 minutes. Transfer to a mixing bowl and refrigerate until completely cool, at least 1 hour.

Once cooled, remove the quinoa from the refrigerator and add the vegetables, olives, and capers. Toss to combine.

Prepare the dressing by whisking together the olive oil, lemon juice, vinegar, mustard, oregano, parsley, and red pepper flakes. Pour the dressing over the salad and mix until all ingredients are evenly coated. Season to taste with salt and pepper.