Preheat the grill to medium-high heat. Brush chicken breasts with olive oil and season with salt and pepper.
Grill chicken for about 6-7 minutes on each side or until fully cooked. Let it rest for 5 minutes, then slice.
To make the dressing, blend Greek yogurt, lemon juice, Dijon mustard, olive oil, garlic, parsley, chives, salt, and pepper until smooth.
In a large bowl, combine lettuce, cherry tomatoes, avocado, red onion, and feta cheese.
Top the salad with grilled chicken slices and drizzle with green goddess dressing before serving.