Trim visible fat from the pork and season it with salt and pepper. Place the onions in a 4-5 quart crockpot; place the meat on top.
Pour 1/2 cup barbecue sauce over the meat. Cover crockpot and cook on low for 9 to 10 hours.
Remove the cooked meat from the crockpot. Drain the juices from the pot, reserving the onions. Coarsely shred the meat into chunks, using two forks. Put the shredded meat and onions back in the crockpot, mix in the remaining barbecue sauce, and cover and cook on low for about one hour. Serve on sliced and toasted rolls. Coleslaw makes the perfect side dish!