In a small cup or bowl combine the seasoning packets and mix well. Rub roast with combined seasonings, wrap in plastic wrap and refrigerate overnight. Heat oil in the pressure cooker over medium-high heat with the lid open. Brown the roast on all sides in the hot oil.
Sprinkle remaining seasonings over the roast in pressure cooker. Pour in the beef broth and add the chopped onion. Seal and lock pressure cooker, and cook over high heat to build pressure until the indicator sounds. Turn heat down to medium, and cook for 45 minutes. Remove from heat and let stand for 5 minutes. Run under cold water to help release the pressure before unsealing the lid. You can use the juices as an au jus, or thicken with flour or cornstarch to make a delicious gravy.