This oven baked 4-ingredient onion and potato layer bake is one of those simple comfort dishes that feels much more special than the short ingredient list would suggest. Thin slices of potato and onion bake together into soft, creamy layers with a beautifully golden top, making it a dependable choice for potlucks, holiday tables, or an easy family supper side when you want something cozy, filling, and budget-friendly.
Serve this bake alongside roast chicken, ham, meatloaf, pork chops, or simple grilled sausages for a satisfying meal. It also pairs nicely with a crisp green salad, steamed green beans, or buttery peas to balance the richness, and for a potluck table it fits right in beside baked beans, deviled eggs, and other classic comfort food favorites.
Oven Baked 4-Ingredient Onion and Potato Layer Bake
Servings: 6 to 8
Ingredients
2 pounds potatoes, peeled and thinly sliced
1 large onion, thinly sliced
1 can (10.5 ounces) condensed cream of mushroom soup
1 1/2 cups milk
Directions
1. Preheat your oven to 375°F and lightly grease a medium casserole dish. In a bowl, whisk together the condensed soup and milk until smooth.
2. Arrange a layer of sliced potatoes in the bottom of the casserole dish, then add a light layer of sliced onion. Spoon some of the soup mixture over the top. Repeat the layers until all ingredients are used, finishing with soup mixture on top.
3. Cover the dish tightly with foil and bake for 60 minutes, or until the potatoes are tender when pierced with a knife.
4. Remove the foil and continue baking for 20 to 25 minutes, until the top is bubbly and golden brown. Let the bake rest for 10 minutes before serving so the layers can settle.
5. Scoop and serve warm as a hearty side dish.
Variations & Tips
For extra richness: Swap part of the milk for half-and-half if you want an even creamier texture. This is a nice trick for holiday meals when you want the casserole to feel especially indulgent.
For more flavor: If your family enjoys a little extra seasoning, add a sprinkle of salt, black pepper, or garlic powder between the layers. Even though this is a four-ingredient version, a little pantry seasoning can really wake it up.
For picky eaters: Slice the onions very thin so they melt right into the casserole as it bakes. That way you still get the sweet onion flavor without noticeable chunky pieces.
For easier slicing: Try to keep the potato slices evenly thin so the bake cooks at the same rate throughout. A mandoline makes quick work of this, but a sharp knife works just fine too.
Make-ahead tip: You can assemble the casserole a few hours ahead, cover it, and refrigerate until baking time. If it goes into the oven cold from the refrigerator, add a little extra baking time so the center gets fully tender.