Lightly grease a 4–6 quart slow cooker. Spread the cubed potatoes evenly at the bottom so they cook in the hottest part of the pot.
Step 2: Add the Meatballs
Place frozen meatballs directly on top of the potatoes. Do not thaw—this keeps them from overcooking or getting mushy.
Step 3: Whisk the Gravy
In a medium bowl, whisk together the cream of mushroom soup, beef broth, and onion soup mix until smooth. Pour over the meatballs and potatoes. Gently nudge with a spoon so the liquid reaches the potatoes, but don’t stir everything together yet.
Step 4: Slow Cook
Cover and cook on LOW for 6–8 hours or HIGH for 3–4 hours, until the potatoes are fork-tender.
Step 5: Final Stir
Gently stir the stew to mix the potato starches into the sauce, creating a thick, glossy gravy. Adjust consistency with a splash of broth if too thick, or cook uncovered on HIGH 15–20 minutes if too thin.
Step 6: Serve
Ladle into bowls. The onion soup mix usually provides enough salt—finish with a little black pepper if desired.
