Rinse and drain quinoa in a fine mesh strainer. Place quinoa, 1¾ cups water and ½ teaspoon salt into a medium saucepan and bring the mixture to a boil. Once boiling, reduce heat to simmer, cover and let it cook for 15 minutes.
Remove from heat, cover, and let the quinoa rest for 5 minutes, to give it time to fluff up.
While the quinoa cooks, prepare the lemon dressing. In a large bowl, mix together the lemon juice, garlic, oregano and sea salt. Let sit 5 minutes, whisk in the olive oil.
Add the chopped red onions, to marinate a little which tames the raw taste. This step is optional, you can add the onions later with the rest of the vegetables if you prefer.
Once the quinoa is cooked, add it to the bowl with the dressing. Toss to thoroughly combine and allow the quinoa to absorb the lemon dressing. Let it cool completely before adding the vegetables.
While the quinoa is cooling prepare the vegetables: Chop the pepper. Cut the cucumber in half lengthwise then into quarters, and then slice. Chop the parsley and measure. Rinse and drain the chickpeas.
Once the quinoa is cool, add the chickpeas, vegetables and parsley, but not the arugula.
Toss until the mixture is thoroughly combined. Season with black pepper to taste, and add an extra pinch of salt if necessary. Let the salad rest for 5 minutes.
Add the arugula right before serving.
Serve chilled or at room temperature.
This salad keeps well in the refrigerator, covered, for about 4-5 days without the arugula, 2-3 days with the arugula. (see note above).