In a small bowl, combine the brown sugar, paprika, salt, pepper, onion powder, and garlic powder together.
Trim off excess skin or gristle if needed and pat the chicken dry with paper towels. Rub the spice mixture evenly over the chicken thighs, on both sides.
Place the onion slices in the slow cooker in an even layer. Lay the seasoned chicken thighs on top of the onion slices.
Place the lid on the slow cooker and cook on high for 2 hours or on low for 4 hours or until the chicken thighs reach 162-165℉.
After the chicken has cooked, remove the chicken from the slow cooker and place it on a sheet pan lined with foil. Brush the top of the chicken with BBQ sauce. Broil for 2-3 minutes or until crispy. Remove the chicken from the broiler, flip, brush the other side with BBQ sauce, and return to the broiler for 2-3 minutes, or until crispy.
Serve with additional BBQ sauce.
Video
Notes
Note On Cooking Time: All crockpots cook at different times and temperatures. My slow cooker only takes about 2 hours on high, but yours may take longer. Take a peek at your chicken thighs after 1 hour and 30 minutes. Once your chicken thighs reach, 165 degrees Fahrenheit, they are cooked to a safe temperature.Storage: Leftover BBQ Chicken can be stored in an airtight container in the refrigerator for up to 3 days or frozen in a freezer-safe container for up to 1 month.