Preheat your grill or grill pan over medium-high heat.
In a small bowl, mix together the olive oil, dried oregano, garlic powder, salt, and pepper. Brush this mixture over the chicken breasts.
Grill the chicken for about 6-7 minutes per side, or until fully cooked and the internal temperature reaches 165°F. Remove from the grill and let it rest for 5 minutes before slicing.
In a large bowl, combine the cooked quinoa, cherry tomatoes, cucumber, red bell pepper, red onion, feta cheese, olives, and parsley.
Squeeze the lemon juice over the mixture and toss gently to combine.
Divide the quinoa salad among serving bowls and top with sliced grilled chicken.