Spinach Casserole

Spinach Casserole is the dish I bring when the sides need to do as much work as the main. Frozen spinach and a few things already in the fridge turn into something rich and cheesy that holds its own on a crowded holiday table.

The filling is cottage cheese and sour cream folded through garlicky spinach, baked under mozzarella, Parmesan, and crunchy onions until the top is golden and the edges bubble. It comes together fast, it reheats well, and it’s just as happy as a vegetarian main as it is next to everything else on the plate.

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Why You’ll Love This Recipe

• The filling gets its body from cottage cheese and sour cream, so you don’t need a can of condensed soup or a flour roux to make it creamy.
• You cook the spinach down in the skillet first, which drives off the water that turns most spinach casseroles into a puddle.
• It’s an assemble-ahead dish: get it into the baking dish, then bake it when the oven is free, which is the whole game on a holiday.
• The crunchy onions on top give you a crisp contrast against the soft filling, and they’re the one part worth adding right at the end.
• One skillet and one baking dish, so it’s less to wash up after a big meal.

Ingredients You’ll Need

You’ll need all the ingredients shown in the photograph below.

Spinach. Fresh or frozen both work. Frozen is what I usually keep on hand for this, and it needs to be thawed and squeezed dry hard before it goes near the skillet, because any water it holds ends up in the casserole. Five cups of chopped spinach cooks down to much less than it looks.

Cottage cheese and sour cream. These are the base, and together they give you a creamy filling without a roux. Let them sit out for about fifteen minutes first, so they blend into the warm spinach smoothly instead of seizing up.

Mozzarella and Parmesan. The mozzarella is what stretches when you scoop, and the Parmesan browns and adds the sharper, saltier note on top. They go on the surface, not stirred through.

Crunchy onions. Optional, but they’re the texture on an otherwise soft dish. Add them right before baking, so they don’t sit and go soft.

How to Make Spinach Casserole

A complete printable recipe and the measurements in both US customary and metric are available in the recipe card below.

Preheat and Prep

Heat the oven to 375°F (190°C) so it’s ready when the filling is. Have your baking dish nearby.

Sauté the Garlic

Melt the butter in a large skillet over medium heat, add the minced garlic, and cook just until fragrant. Don’t let it brown, or it turns bitter.

Wilt the Spinach

Stir in the spinach and cook until it’s wilted and the excess moisture has cooked off. This is the step not to rush. If there’s liquid pooling in the pan, keep going until it’s gone, because that water is what makes a casserole watery.

Mix the Filling

Take the skillet off the heat, then stir in the cottage cheese, sour cream, salt, and pepper. Mixing off the heat keeps the dairy from splitting. Stir until it looks smooth and creamy.

Assemble the Casserole

Spread the spinach mixture evenly in the baking dish, then top with the mozzarella, Parmesan, and crunchy onions if you’re using them.

Bake Until Golden

Bake for 20 to 25 minutes, until the top is golden and the edges are bubbling. Start checking around the 20-minute mark, since ovens run differently.

Rest, Then Serve

Let it cool for a few minutes before serving so the filling sets enough to scoop cleanly.

Recipe Notes and Expert Tips

• Dry the spinach harder than feels necessary. Fresh or frozen, moisture is what makes this watery. Cook off the liquid in the skillet, and with frozen spinach, squeeze it dry before it even goes in the pan.
• Bring the dairy to room temperature. Cottage cheese and sour cream straight from the fridge blend unevenly into warm spinach. Fifteen minutes on the counter fixes it.
• Season the filling properly. Spinach and mild dairy need a generous pinch of salt and pepper, or the whole thing tastes flat.
• Onions go on last. Add the crunchy onions right before the dish goes in the oven so they stay crisp instead of soaking up steam.

Recipe Variations

• Stir in half a cup of sautéed mushrooms with the spinach for a deeper, more savory filling. Mushrooms bring their own water, so cook them down fully first. I haven’t tested this exact amount here, so treat it as a starting point.
• Swap the crunchy onions for panko toasted in a little butter if you want the crisp top without the fried-onion flavor. This changes the topping’s taste more than its texture. It isn’t tested in this recipe.

How to Store Leftovers

Let leftovers cool for a short while, then cover and refrigerate within two hours of baking. They keep for up to 4 days in an airtight container, which holds the filling and keeps the topping from drying out. To reheat, warm individual portions in a microwave in 30-second bursts, or cover the dish with foil and reheat in a 325°F oven until hot through.

To freeze, let the baked casserole cool, then refrigerate it until cold before wrapping the dish tightly in plastic and foil, or portioning it into freezer-safe containers. It keeps for up to 2 months. Thaw overnight in the fridge and reheat in a 350°F oven until hot through and bubbling again.

What to Serve With Spinach Casserole

It wants something bright alongside it, since the filling is rich. A simple green salad with a sharp vinaigrette does the job, and so does a bowl of roasted tomato soup for scooping and dipping crusty bread into.

If you want to build it into a bigger vegetarian spread, I put it next to a vegetable pasta or a plate of spaghetti aglio e olio, both of which carry the meal without competing with the casserole. Roasted asparagus or broccoli on the side rounds out the plate.

More Easy Casseroles for Your Table

If this is your kind of dish, here are a few more casseroles I’d put on the same table.

• My broccoli casserole is the one I make when I want something that bakes up cheesy with real bite to the vegetables.
• The green bean casserole shares those crunchy onions on top, so it’s a natural match here.
• For something with more heft, the wild rice casserole brings a nutty, chewy base.
• The cauliflower casserole gives you a crisp panko-and-Parmesan top over a creamy sauce.