1. Preheat your grill to medium-high heat.
2. In a small bowl, mix olive oil, dried oregano, garlic powder, salt, and pepper. Rub this mixture all over the chicken breasts.
3. Grill the chicken for about 6-7 minutes on each side or until fully cooked. Let it rest for a few minutes before slicing.
4. In a large mixing bowl, combine romaine lettuce, cherry tomatoes, cucumber, red onion, kalamata olives, and feta cheese.
5. In a small bowl, whisk together olive oil, red wine vinegar, dried oregano, minced garlic, salt, and pepper to make the dressing.
6. Pour the dressing over the salad and toss to combine.
7. Top the salad with the sliced grilled chicken and serve immediately.