In a small bowl, combine the 1 tablespoon brown sugar, 1 tablespoon smoked paprika, 1 teaspoon kosher salt, ½ teaspoon black pepper, 1 teaspoon onion powder, and 1 teaspoon garlic powder together.
Trim off excess skin or gristle if needed from 2-3 pounds bone-in chicken thighs and pat the chicken dry with paper towels. Rub the spice mixture evenly over the chicken thighs, on both sides.
Place 1 large yellow onion thinly sliced 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 185℉ for tender, yet juicy results.
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 slow cookers 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. Aim for an internal temperature between 185℉-190℉ for juicy, tender results. 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.