Add the frozen meatballs: Place the fully cooked frozen meatballs into the Instant Pot. There is no need to thaw them first.
Add the liquid: Pour the beef broth and pepperoncini juice around the meatballs.
Add the seasonings: Sprinkle the ranch seasoning and au jus gravy mix evenly over the meatballs.
Add butter and peppers: Cut the butter into smaller pieces and distribute it over the meatballs. Add the pepperoncini peppers.
Pressure cook: Secure the Instant Pot lid and cook according to the recipe's specified pressure-cooking time.
Release the pressure: Allow the pressure to release according to your Instant Pot method before carefully opening the lid.
Coat the meatballs: Stir the meatballs gently so the buttery gravy coats them evenly.
Adjust the sauce: Let the sauce stand briefly. If it is thinner than preferred, use the sauté function with the lid off for a short time to reduce it.
Serve: Serve warm over mashed potatoes, rice, or egg noodles, or serve with toothpicks as an appetizer.