Gather your ingredients: Lay out the beef, butter, and onion soup mix to make assembly a breeze.
Layer in your slow cooker: Place the beef stew meat in the slow cooker, then dot the butter evenly over the top.
Add the seasoning: Sprinkle the dry onion soup mix over everything.
Cook it low and slow: Cover and cook on Low for 8 hours or High for 4-5 hours. Stir once or twice if you’re around, though it’s not necessary.
Serve and enjoy: Spoon the tender beef onto plates and drizzle some of that buttery sauce over the top. Serve hot with your favorite side dishes!