Combine pot roast seasoning and then season beef. Here we're using garlic powder, onion powder, oregano, and brown sugar.
Use the sauté feature to cook onions for 3-4 minutes. Remove and sear beef for 3-4 minutes on each side.
Deglaze Instant Pot with the sauce ingredients and scrape the bottom. Then, add veggies and beef. Cook on high pressure for 90 minutes.
Remove beef from Instant Pot and the veggies. Cook on high pressure for 2 minutes. Meanwhile, shred beef.
Remove veggies from Instant Pot and use cornstarch to thicken gravy. Serve Pot Roast with gravy immediately.