Why You’ll Love Spinach and Mushroom Casserole Recipe

The earthy mushrooms and tender spinach pair beautifully, offering a rich but not heavy flavor.
It’s simple and straightforward — few ingredients, minimal fuss, and big on taste.
Ready in about 40 minutes, making it a great option for weekday dinners or when you want something cozy without a long prep.
The melted cheddar gives the dish a creamy, satisfying finish that’s universally appealing.

Ingredients

(Tip: You’ll find the full list of ingredients and measurements in the recipe card below.)

2 tablespoons butter
1 pound fresh mushrooms, sliced
2 (10‑ounce) packages fresh spinach, rinsed and stems removed
1 teaspoon salt
4 tablespoons butter, melted
¼ cup finely chopped onion
1½ cups shredded cheddar cheese, divided

Directions

Preheat the oven to 350 °F (175 °C). Grease a 2‑quart casserole dish.
In a large skillet over medium heat, melt the 2 tablespoons butter and sauté the mushrooms until tender (about 8–10 minutes).
Meanwhile, wilt the spinach in a large pot over medium heat; drain well, pressing out excess water. Place the drained spinach in the prepared baking dish.
Sprinkle the spinach with the salt, pour the 4 tablespoons melted butter over it, then add the chopped onion and half of the shredded cheddar cheese.
Layer the sautéed mushrooms on top, then sprinkle with the remaining cheddar cheese.
Bake in the preheated oven for about 20 minutes, until the cheese is melted and the casserole is heated through.
Remove from oven and let stand a few minutes before serving.

Servings and timing

Servings: 6
Prep time: 20 minutes
Cook time: 20 minutes
Total time: about 40 minutes

Variations

For a richer dish: substitute half the cheddar with Gruyère or mozzarella for extra meltiness.
Add garlic: sauté 1–2 cloves of minced garlic with the mushrooms for added flavor.
Make it vegetarian‑cheese‑free: omit the cheese and stir in a non‑dairy cheese or nutritional yeast instead.
Add protein: for a fuller main dish, stir in cooked diced chicken or crumbled sausage before baking.
Spice it up: add a pinch of red pepper flakes or smoked paprika to the mushrooms for a little heat and smokiness.

Storage/Reheating

Storage: Cover and refrigerate the casserole for up to 2–3 days.
Reheating: Reheat in a 350 °F (175 °C) oven for about 10–15 minutes (cover loosely if the cheese is already golden) until warmed through. Alternatively, portion individual servings and reheat in the microwave for 1–2 minutes until hot.
Freezing: You can assemble and freeze before baking — then bake from frozen, adding a few extra minutes to cook time. After baking, leftovers freeze well in individual portions for about 1–2 months; thaw overnight in the fridge before reheating.

FAQs

What size casserole dish should I use?

A 2‑quart (about 8″×8″ or equivalent) casserole dish is ideal for layering and baking this recipe.

Can I use frozen spinach instead of fresh?

Yes, you can. Use about 20 ounces of frozen spinach (thawed and well drained) instead of fresh. Reduce the wilt step since it’s already cooked, and be sure to squeeze out as much moisture as possible to avoid a watery casserole.

What type of mushrooms work best?

Common button or cremini mushrooms work beautifully. You can also use a mix of wild mushrooms like shiitake or portobello for deeper flavor.

Can this dish be made ahead of time?

Absolutely. You can prepare the casserole, cover and refrigerate it unbaked for a few hours before baking. When ready, bake as directed; you may need to add a few extra minutes.

Is this recipe gluten‑free?

Yes — as written, the recipe is naturally gluten‑free (no flour or wheat ingredients). Just ensure your cheese and other packaged items are certified gluten‑free if needed.

Can I make this with reduced‑fat cheese or butter?

Yes — you can reduce the butter slightly or use reduced‑fat cheddar. The texture might be a bit lighter and less creamy, but it still works.

What side dishes go well with this casserole?

This dish pairs nicely with roasted meats like beef or chicken, steamed vegetables, or a simple green salad. It works equally well as a side or light main.

How can I avoid the casserole becoming too watery?

Make sure to thoroughly drain both the wilted spinach and sautéed mushrooms. Excess moisture is the usual culprit for a watery bake. You might also let the dish rest for 5 minutes before serving so juices settle.

Can I add other vegetables to this recipe?

Yes — chopped bell peppers, zucchini slices, or diced tomatoes would integrate well. Just sauté or cook them appropriately before layering.

How do I get a golden, slightly crisp cheese topping?

If you’d like a golden top, switch the oven to broil for the last 1–2 minutes of baking—just watch closely so the cheese doesn’t burn.

Conclusion

This Spinach and Mushroom Casserole brings together wholesome greens, savory mushrooms and gooey cheddar in a simple, yet satisfying bake. Whether you serve it as a side‑dish alongside roast meats or enjoy it as a meat‑free main, it stands out for its ease, comforting textures and rich flavor without being overly heavy. With flexible variations and make‑ahead convenience, it’s a reliable go‑to for busy kitchens and cozy dinners alike.