In a medium saucepan, combine the rinsed quinoa and water. Bring to a boil over medium-high heat. Once boiling, reduce the heat to low, cover, and simmer for about 15 minutes or until the quinoa is fluffy and the water is absorbed. Remove from heat and let it sit covered for 5 minutes. Fluff with a fork and allow to cool.
In a large bowl, combine the diced apple, chopped celery, dried cranberries, walnuts, feta cheese (if using), and parsley.
In a small bowl, whisk together the olive oil, apple cider vinegar, honey, salt, and pepper until well combined.
Add the cooled quinoa to the large bowl with the other ingredients. Pour the dressing over the salad and toss gently to combine.
Serve immediately or refrigerate for 30 minutes to allow the flavors to meld.