Heat oil in the pressure cooker using the BROWN setting. Add the roast and evenly brown all sides. Add onions and celery and cook for 1 minute. Take out the roast. Put in the barbecue sauce, beer, and chili powder. Mix well. Place the roast back in the pressure cooker. Cover and set to high pressure. Cook for 60 minutes.
Release the pressure using the quick-release method. When the pressure has dropped, unlock and remove cover. Test the roast for tenderness with a fork. If not tender, cover and cook under pressure for an additional 10 minutes. Remove the roast and let sit for at least 15 minutes. Slice thin against the grain. Serve with barbecue sauce.
Recipe courtesy of Deni, Reprinted with permission.