In a large bowl, combine the buttermilk, ranch seasoning mix, garlic powder, onion powder, and black pepper. Add the chicken cubes and stir to coat evenly. Cover and refrigerate for at least 1 hour, or up to overnight for best flavor.
Preheat your grill to medium-high heat. If using wooden skewers, soak them in water for 30 minutes to prevent burning.
Remove the chicken from the marinade and thread the cubes onto the skewers, leaving a little space between each piece.
Brush the skewers lightly with olive oil and sprinkle the grated Parmesan cheese over the chicken.
Place the skewers on the grill and cook for 10-12 minutes, turning occasionally, until the chicken is cooked through and has nice grill marks. The internal temperature should reach 165°F.
Remove the skewers from the grill and let them rest for a few minutes before serving. Enjoy with your favorite dipping sauce or a side salad.