Rinse quinoa in a fine mesh strainer under cold water for a couple of minutes.
In a pot, combine rinsed quinoa and water; bring to a boil over high heat.
Reduce heat to low, cover, and simmer for about 15 minutes until quinoa is fluffy and water is absorbed.
Remove from heat and let quinoa sit for 5 minutes, then fluff with a fork.
While quinoa cools, prepare the vegetables: chop tomatoes, cucumber, bell pepper, and onion.
In a large bowl, combine cooked quinoa and chopped vegetables; mix gently.
Add olives, feta, and parsley, stirring to combine evenly.
In a small bowl, whisk together olive oil, red wine vinegar, salt, and pepper; pour over the salad.
Gently toss the salad to coat all ingredients with the dressing.
Taste and adjust seasoning if necessary; serve immediately or refrigerate for an hour before serving.
