Rinse the quinoa under cold water, then combine with 0.5 cup water in a small pot; bring to a boil, cover, and simmer for 15 minutes until the water is absorbed.
In a small bowl, whisk together the olive oil, lemon juice, lemon zest, minced garlic, oregano, salt, and pepper to create the dressing.
Place the chicken breast in a shallow dish and coat with half of the prepared dressing, letting it marinate for 10 minutes.
Heat a non-stick skillet over medium-high heat and sear the chicken for 6-7 minutes per side until golden brown and the internal temperature reaches 165°F.
While the chicken rests, toss the cooked quinoa with the remaining dressing, diced cucumber, halved cherry tomatoes, and chopped fresh parsley.
Slice the chicken into thin strips and serve it over the vibrant quinoa salad for a bright and satisfying lunch.