Rinse the quinoa under cold water, then combine with 0.5 cup water in a small pot; bring to a boil, reduce to low, cover, and simmer for 15 minutes until water is absorbed.
Season the chicken breast with half of the sea salt, black pepper, and dried oregano.
Heat a grill pan or skillet over medium-high heat and cook the chicken for 6-7 minutes per side until the internal temperature reaches 165°F.
While the chicken cooks, whisk together the extra virgin olive oil, lemon juice, and the remaining salt, pepper, and oregano in a large mixing bowl to create the vinaigrette.
Dice the cucumber, halve the cherry tomatoes, finely mince the red onion, and chop the fresh parsley.
Once the chicken is cooked, let it rest on a cutting board for 5 minutes before slicing into bite-sized strips.
Add the cooked quinoa, prepared vegetables, and sliced chicken to the mixing bowl with the vinaigrette; toss thoroughly to combine and serve immediately.