Heat 1 tbsp of vegetable 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. Add barbecue sauce, beer, and chili powder and mix well. Place the roast back in the pressure cooker.
Cover and lock lid. Turn the regulator knob to pressure and select HIGH cooking mode to cook for 60 minutes.
Release pressure by using the quick-release method. When the pressure has dropped, unlock and remove the lid.