In a medium saucepan, combine the rinsed quinoa and 2 cups of water. Bring to a boil over medium-high heat.
Once boiling, reduce heat to low, cover, and simmer for 15 minutes or until the water is absorbed and quinoa is tender.
Remove from heat and let quinoa sit covered for 5 minutes, then fluff with a fork and transfer to a large mixing bowl to cool.
While quinoa is cooking, season the chicken breasts with 1/2 teaspoon salt and 1/4 teaspoon black pepper.
Heat 1 tablespoon olive oil in a skillet over medium heat.
Add the chicken breasts and cook for 6-7 minutes per side or until fully cooked and internal temperature reaches 165°F (74°C).
Remove chicken from skillet and let rest for 5 minutes, then dice into bite-sized pieces.
Add the diced chicken, cherry tomatoes, cucumber, red onion, parsley, and feta cheese to the cooled quinoa in the mixing bowl.
In a small bowl, whisk together the lemon juice, extra virgin olive oil, Dijon mustard, garlic powder, and a pinch of salt and black pepper.
Pour the dressing over the salad and toss gently to combine all ingredients evenly.
Serve immediately or refrigerate for up to 2 days for flavors to meld.