Season the chicken breast evenly with half of the dried oregano, sea salt, and black pepper.
Heat a non-stick skillet over medium-high heat and cook the chicken for 6-7 minutes per side until golden brown and cooked through.
While the chicken is cooking, dice the cucumber into small cubes and halve the cherry tomatoes.
In a small mixing bowl, whisk together the extra virgin olive oil, fresh lemon juice, and the remaining oregano, salt, and pepper to create the dressing.
Remove the chicken from the pan, let it rest for 2 minutes, then slice it into thin strips or bite-sized pieces.
In a serving bowl, combine the cooked quinoa, diced cucumber, and halved cherry tomatoes.
Place the sliced chicken on top of the quinoa mixture, sprinkle with crumbled feta cheese, and drizzle the lemon-herb dressing over the entire bowl before serving.