Season the chicken breast with half of the sea salt, black pepper, and dried oregano.
Grill the chicken over medium-high heat for 6-7 minutes per side until the internal temperature reaches 165°F.
While the chicken rests, whisk together the extra virgin olive oil, lemon juice, and the remaining sea salt, black pepper, and oregano in a large mixing bowl.
Add the cooked quinoa, diced cucumber, halved cherry tomatoes, and minced red onion to the bowl with the dressing.
Toss the salad thoroughly until all ingredients are evenly coated and vibrant.
Slice the grilled chicken into thin strips.
Divide the quinoa salad into serving bowls, top with the sliced chicken, crumble the feta cheese over the top, and garnish with fresh parsley.