Heat the oil in a large stock pot over medium high heat.
Season the meat generously with salt and pepper. Add the meat to the oil and cook until browned, about 5-7 minutes. You may need to brown the beef in batches to get a good sear. If so, drain any accumulated grease between batches.
Add the onion, bell peppers and mushrooms to the pot and sauté until tender, about 3-5 minutes.
Add the garlic and sauté for 30 seconds.
Add the broth to the pot and scrape up any browned bits from the bottom of the pan.
Add the pepperoncini peppers, butter, and brown gravy mix. Stir to combine.
Bring the broth to a boil, then cover the pot and reduce the heat to low. Simmer for 1 hour and 15 minutes.
Remove the lid and let the liquid simmer for an additional 15 minutes to thicken up the gravy.
Remove the pepperoncini peppers before serving. Discard the pepper or remove the stems, chop them up and add them back into the pot.
Season the beef tips with salt and pepper to taste. Serve over hot egg noodles, rice or mashed potatoes.
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Notes
Storage. Braised beef tips with gravy should be stored in an airtight container in the refrigerator within two hours. Consume within 3-5 days.Freezing. Transfer the beef tips to an airtight freezer container or freezer bag. Be sure to leave some room for expansion. If using a freezer bag, fold the top of the bag over to remove excess air. Consume within three months.Reheating. If frozen, allow the beef tips to thaw in the refrigerator overnight. Transfer to a medium saucepan, cover and simmer over medium low heat until the gravy is bubbling and the beef tips are heated through. Cooking over low heat rather than high heat prevents the beef tips from becoming overcooked and mushy.