Line the slow cooker with a slow cooker liner if desired.
In a medium mixing bowl combine brown sugar, salt, pepper, and onion powder. Mix well, Add Italian dressing, and 1/4 cup barbecue sauce, and mix again.
Add one layer of ribs to the slow cooker at a time. If you need to trim your ribs to get them to fit it's okay. I don't recommend cutting them when grilling them or cooking them quickly, but for this recipe it's going to be so tender that cutting a slab in half to fit the slow cooker is okay. Scoop a big dollop of the sauce over that layer, then repeat with each layer. Ribs, sauce, ribs, sauce, that way each layer is covered in the sauce mixture.
Place the lid on the slow cooker and cook for about 7 to 8 hours on low. Every slow cooker is a bit different so start checking yours at the 6 hour mark and make adjustments as needed. Mine took 7 hours to become fully tender.
Remove from the slow cooker and drain excess liquid.