01 - In a large mixing bowl, combine the barbecue sauce, olive oil, apple cider vinegar, brown sugar, smoked paprika, garlic powder, onion powder, salt, and black pepper. Whisk until smooth and well blended.
02 - Measure out ¼ cup of the marinade mixture and set aside in a small bowl for basting during grilling.
03 - Add the chicken thighs and drumsticks to the remaining marinade, turning to coat each piece thoroughly. Cover the bowl with plastic wrap and refrigerate for at least 1 hour, or up to overnight for more pronounced flavor.
04 - Preheat an outdoor grill to medium-high heat (approximately 375–400°F). Lightly oil the grates using a folded paper towel dipped in vegetable oil to prevent sticking.
05 - Remove the chicken from the marinade, allowing any excess to drip off. Place the pieces skin-side down on the hot grill. Cook for 6–8 minutes per side, brushing with the reserved basting sauce and turning occasionally, until the skin is deeply charred and an instant-read thermometer inserted into the thickest part registers 165°F.
06 - Transfer the grilled chicken to a platter and let rest for 5 minutes to allow juices to redistribute. Garnish with chopped fresh parsley if desired and serve immediately.