Pat the chicken breasts dry with a paper towel. Drizzle with olive oil and season with oregano, garlic powder, salt, and pepper. Preheat grill or skillet to medium-high heat for 5 minutes. Grill chicken for 6-7 minutes on each side until the internal temperature reaches 165°F. Let rest for 5 minutes before slicing.

In a large mixing bowl, chop cucumber, halved cherry tomatoes, and sliced red onion. Add crumbled feta and pitted Kalamata olives. Drizzle with lemon juice and toss gently until well combined.

Divide the prepared salad among serving bowls. Layer sliced chicken on top and garnish with chopped parsley. Serve immediately.