Preheat the oven to 400ºF with a rack in the center of the oven. Line a rimmed baking sheet with parchment paper.
Set chicken into a mixing bowl (or zip-top bag). Drizzle with oil and season with salt, pepper, onion, and garlic powder. Mix until evenly coated with seasonings.
Pour half of the bbq sauce over the chicken and stir to evenly coat. Arrange chicken thighs on a baking sheet with the smooth side down.
Bake for 20 minutes then flip the chicken over, brush with the remaining bbq sauce, and bake for another 10 minutes or until the internal temperature reaches at least 165°F on an instant-read thermometer.
Set the oven to broil and continue baking for 3-5 minutes to caramelize and set the bbq sauce. Keep an eye on it so it doesn’t burn. Rest for at least 5 minutes then serve with more bbq sauce if desired.