01 - Whisk together olive oil, barbecue sauce, smoked paprika, garlic powder, onion powder, salt, and black pepper in a bowl. Add chicken cubes and toss thoroughly to coat. Cover and refrigerate for at least 15 minutes to marinate.
02 - Combine mayonnaise, sour cream, chives, parsley, dill, garlic, lemon juice, salt, and pepper in a bowl. Whisk until smooth and blended. Gradually stir in 2-3 tablespoons milk until desired consistency is reached. Refrigerate until serving.
03 - Heat grill or grill pan to medium-high temperature, approximately 375-400°F.
04 - Thread marinated chicken cubes onto skewers, leaving slight space between pieces for even cooking.
05 - Place skewers on preheated grill and cook for 8-9 minutes per side, turning once, until chicken reaches internal temperature of 165°F and develops light char marks.
06 - Arrange mixed greens, cherry tomatoes, cucumber, red onion, avocado, and crumbled feta on a large serving platter or divide among individual plates.
07 - Place hot grilled chicken skewers over the salad. Drizzle generously with herby ranch dressing and serve immediately while chicken is warm.