In a medium pot, combine rinsed quinoa and water (or chicken broth). Bring to a boil, then reduce heat to low, cover, and simmer for about 15 minutes or until liquid is absorbed. Fluff with a fork and allow it to cool.
Season chicken breasts with olive oil, salt, pepper, dried oregano, and dried thyme.
Heat a skillet over medium heat and cook the chicken for about 6-7 minutes on each side, or until fully cooked and no longer pink in the center. Remove from heat and let it rest for a few minutes before slicing.
In a large bowl, combine the cooled quinoa, diced cucumber, halved cherry tomatoes, and red onion.
Add the sliced chicken on top. Then drizzle with lemon juice, lemon zest, and a sprinkle of feta cheese if using. Toss everything gently until combined.
Adjust seasoning with additional salt and pepper if needed.
Garnish with freshly chopped parsley before serving.