Turn the Instant Pot to saute and let heat until it reads HOT, or for 2-3 minutes.
Add in 1 teaspoon of the oil. Pierce each sausage several times with a fork and then place the sausage into the oil and sear on each side until browned, about 2 minutes per side. Once browned, remove the sausage from the inner pot and place them onto a clean plate.
With the pressure cooker still on the saute setting, add in an additional teaspoon of oil, along with the sliced peppers and onions. Saute for 3-4 minutes or until the vegetables have begun to soften. Turn the Instant Pot off.
Add in the stock, and use a wooden spoon to scrape up any browned bits on the bottom of the inner pot.
Add the sausage back to the inner pot. Add in the garlic and then spoon the tomato sauce over the sausage.
Set to cook on high pressure for 6 minutes. Once the cooking time has elapsed, allow the pressure to release naturally on its own for at least 10 minutes.
Serve on buns, over pasta or rice, or as a stand-alone meal.
Notes for using an 8-quart model: 1 cup of stock is still enough liquid for this recipe, as the onions and peppers will give off more liquid as they cook.Feel free to omit the peppers, onions, garlic, and/or tomato sauce if desired. For the sausage, use any brand or variety you like of uncooked Italian sausage. Hot, sweet, mild, or turkey, pork, or chicken.Feel free to skip sauteeing the sausages, onions, and peppers and instead just layer the ingredients in the inner pot and cook for 7 minutes on high pressure.In place of the fresh onions and peppers, you can use a 10-ounce bag of frozen peppers and onions. After sauteing the sausage, remove them to a plate, turn the instant pot off, deglaze the pan with stock then add in the frozen peppers and onions, along with the garlic, and tomato sauce and cook for 6 minutes on high pressure.You can double this recipe, or even just opt to throw in a couple of extra sausages with no change to the cooking time. Just keep in mind you may need to brown your sausages in batches.Storage: Leftover Instant Pot Sauage and Peppers can be stored in an airtight container for up to 3 days in the refrigerator. Reheat in the microwave-safe dish covered with a paper towel to prevent splatter in 1-minute intervals until warmed through. You can also opt to freeze the leftovers for up to 3 months in an airtight, freezer-safe container. Defrost in the refrigerator and reheat as desired. Use within 3 days of defrosting.