Set the Instant Pot to Saute and add 1 tablespoon of oil.
Cut chuck roast into 3 large pieces and place in the Instant Pot to sear on all sides.
Press Cancel on the Instant Pot, and scrape the bottom of the liner to deglaze the pot.
Add in the onion, garlic, vinegar, sugar, Worcestershire sauce, and seasonings.
Pour in the stewed tomatoes on top of the chuck roast - Do Not Stir.
Close the lid and set to MANUAL or PRESSURE COOK (Whichever setting your pressure cooker has).
Set timer for 60 minutes.
Once the time is up, allow the pot to Naturally Release for 15 minutes before opening the lid.
Using a slotted spoon, remove the pot roast and veggies.
Serve alone or serve on sandwiches.
Notes
*This recipe uses a 3 lb chuck roast. Pressure cooking times vary. Thawed chuck roasts cook for 20 minutes per pound and frozen chuck roasts cook for 30 minutes per pound. Natural release times stay the same.