If oven roasting, preheat oven to 425 F and position the middle rack. If grilling, preheat your grill to medium-high heat.
Spatchcock the chicken: Using strong kitchen shears, cut through the backbone of the chicken and remove it, along with any little bones that may be sticking out. With the lower side of the palm of your hands, press down the chicken until flattened. Thoroughly pat dry the chicken. Season a few generous drizzles of oil (about 2-3 tablespoons), garlic powder, smoked paprika, Kosher salt, and ground black pepper. chicken with salt, black pepper, and garlic powder. Rub all over the chicken. Clip off the wing tips or tuck them under the skin so that they don't burn.
Set aside ½ cup of the BBQ sauce for brushing the chicken. Reserve the rest of the sauce for serving.
If oven-roasting: In a large sheet pan, roast the chicken for about 30 mins. Remove from oven and brush with some BBQ sauce, and return to oven for 10 minutes. Repeat one more time. It should take about 50 minutes total, or until internal temperature reaches 165 degrees F.
If grilling: Cook on the grill over medium-high heat, skin side down first, flipping every few minutes. Cover with the lid for faster cooking. Once it reaches 155 degrees F (about 45 minutes), baste with BBQ sauce during the last 15 minutes of cooking time, or until it reaches 165 degrees F in the thickest part.
Let the chicken rest for 10 to 15 minutes before carving. Serve with the reserved barbecue sauce. Enjoy!