Turn the Instant Pot to Sauté setting. Season the meat with a pinch of the salt and pepper. When it reads Hot, add the oil, then brown the meat in batches. Remove to a clean plate, and cover to keep warm
Add the chopped onion, carrots, celery and garlic. Add a pinch of salt and pepper, and stir until slightly soft. Deglaze pot with a little beef broth to remove any browned bits
Hit Cancel, to turn pot off. Add the browned beef back to the pot.
Pour in the remaining beef broth and Worcestershire sauce
Add the rinsed barley, and give it a quick stir to make sure it's covered with liquid
Add the diced tomatoes, but do not stir. Add the remaining salt and pepper, plus the dried parsley or Italian seasoning, if using
Place lid on pot, make sure vent is set to sealing (on some models), and hit PRESSURE COOK for 25 minutes
Pot will take a few minutes to reach pressure, then will count down and cook. Allow a 10 minute natural release, then turn valve to quick release remaining pressure
When pot beeps, carefully remove lid, and stir. Add fresh parsley, if desired, and serve