Season the chicken: Add the chicken thighs, BBQ seasoning, and olive oil to a large mixing bowl. Toss until the chicken is evenly coated. Unroll each thigh as you mix so the seasoning gets into the folds.
Arrange the chicken: Place the thighs in a single layer in a broiler-safe baking dish. For boneless chicken thighs, keep each piece spread flat so it cooks evenly. If using bone-in chicken thighs, arrange them skin-side up.
Start baking: Bake the chicken for 15 minutes.
Add the first layer of BBQ sauce: Remove the baking dish from the oven. Brush the thighs with 1/2 cup of BBQ sauce, coating both sides.
Continue baking: Return the chicken to the oven and bake for 15 minutes more.
Add more sauce: Remove the baking dish from the oven and brush the chicken with 1/4 cup of BBQ sauce.
Broil: Broil on high for 2–3 minutes, watching closely, until the BBQ sauce is bubbling and caramelized around the edges.
Finish and serve: Brush the chicken with the remaining 1/4 cup BBQ sauce. Top with chopped parsley, if using, and serve.
Notes
Bone-in option: Bone-in, skin-on chicken thighs work too. After seasoning, arrange them in the pan skin-side up. Add about 5–7 minutes to the baking time, then check the thickest piece for doneness before broiling.
Trim the fat: Remove any large pieces of excess fat before seasoning.
Oil: Avocado oil works in place of olive oil.
BBQ sauce: Use a thick hickory or Kansas City-style sauce for the stickiest finish.
Pan: Use a broiler-safe baking dish.
Doneness: Check the thickest thigh and cook to at least 165°F.
Broiling: Watch closely since BBQ sauce can burn quickly.