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 allow flavors to penetrate.
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 desired consistency. Refrigerate until serving.
03 - Heat grill or grill pan to medium-high temperature, approximately 375-400°F. If using wooden skewers, soak them in water for at least 30 minutes to prevent burning.
04 - Thread marinated chicken cubes onto skewers, leaving slight space between pieces for even cooking. Grill for 8-9 minutes per side, turning once, until internal temperature reaches 165°F and chicken develops light char marks.
05 - Arrange mixed greens as a bed on a large serving platter or individual plates. Distribute cherry tomatoes, cucumber, red onion, avocado, and feta cheese evenly across the greens.
06 - Remove chicken from skewers if desired and place hot pieces atop the salad. Drizzle generously with chilled herby ranch dressing. Serve immediately while chicken is still warm.