01 - Pat chicken thighs completely dry using paper towels to ensure proper seasoning adherence and caramelization.
02 - Whisk together olive oil, apple cider vinegar, brown sugar, smoked paprika, garlic powder, onion powder, chili powder, salt, and black pepper in a large bowl until sugar dissolves.
03 - Add chicken thighs to the bowl and toss thoroughly to coat evenly with the spice mixture. Let marinate for at least 15 minutes, or up to 4 hours refrigerated for deeper flavor penetration.
04 - Preheat grill to medium-high heat or preheat oven to 400°F if baking indoors.
05 - Place chicken thighs skin-side down on the grill. Sear for 6 to 7 minutes until skin begins to crisp and develop golden-brown coloration.
06 - Flip chicken thighs and brush generously with barbecue sauce. Continue grilling for 25 to 30 minutes, turning and basting with additional sauce every few minutes, until internal temperature reaches 175°F and exterior shows slight charring. For oven method, arrange skin-side up on foil-lined baking sheet and roast for 30 to 35 minutes, brushing with sauce every 10 minutes.
07 - Transfer chicken to a cutting board or serving platter and let rest for 5 minutes to allow juices to redistribute throughout the meat.