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 1/4 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 each piece to coat thoroughly. Cover the bowl with plastic wrap and refrigerate for at least 1 hour, or up to overnight for more intense flavor penetration.
04 - Preheat your outdoor grill to medium-high heat (approximately 375°F to 400°F). Lightly oil the grill grates using a paper towel dipped in vegetable oil to prevent the chicken from 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 to 8 minutes per side, brushing with the reserved basting sauce and turning occasionally, until the skin is deeply charred and the internal temperature registers 165°F on a meat thermometer.
06 - Transfer the grilled chicken to a platter and let it rest for 5 minutes to allow the juices to redistribute. Garnish with freshly chopped parsley if desired and serve immediately.