Place the stew meat in a 6-quart slow cooker and season with the black pepper and garlic powder.
Top with the sliced onion and mushrooms.
Add the beef broth, brown gravy mix, Italian dressing mix, Worcestershire sauce, and steak sauce; stir to combine.
Cover and cook on LOW for 7–8 hours or HIGH for 4–5 hours, until the beef is fork tender.
Whisk the cornstarch and cold water together until smooth; stir into the slow cooker.
Cover and cook on HIGH for an additional 20–30 minutes, until the gravy has thickened.
Stir the beef, onions, and mushrooms into the thickened gravy; sprinkle with parsley.
Serve over mashed potatoes, rice, or buttered egg noodles.
Notes
Store leftovers in an airtight container in the refrigerator for up to 4 days, or freeze for up to 2 months. Thaw overnight in the refrigerator before reheating gently on the stovetop or in the microwave.For a gluten-free version, use a gluten-free brown gravy mix and check labels on the Worcestershire sauce, dressing mix, and steak sauce.
All nutritional information provided is an estimate. For specific dietary needs or concerns, we recommend consulting a nutrition calculator or a qualified expert.