01 - Combine olive oil, barbecue sauce, smoked paprika, garlic powder, onion powder, salt, and black pepper in a bowl. Add chicken cubes and toss to coat thoroughly. Cover and refrigerate for at least 15 minutes to absorb flavors.
02 - Whisk together mayonnaise, sour cream, chives, parsley, dill, garlic, lemon juice, salt, and pepper in a separate bowl. Gradually add milk while whisking until you reach your preferred consistency. Refrigerate until serving.
03 - Heat grill or grill pan to medium-high temperature, approximately 400°F. Ensure grates are clean and lightly oiled to prevent sticking.
04 - Thread marinated chicken pieces onto skewers, leaving a small space between pieces for even cooking. Discard any remaining marinade.
05 - Place skewers on the preheated grill. Cook for 8-9 minutes per side, turning once, until chicken reaches an internal temperature of 165°F and develops light char marks.
06 - Arrange mixed salad greens on a large serving platter or individual plates. Top with cherry tomatoes, cucumber slices, red onion, avocado, and crumbled feta if using.
07 - Remove chicken from skewers and place atop the salad, or arrange skewers across the platter. Drizzle generously with chilled herby ranch dressing and serve immediately.