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    Home » Side Dish Recipes

    Cheesy Spinach Mushroom Casserole

    Published: Apr 27, 2020 · Modified: Jun 5, 2023 by Gwen · This post may contain affiliate links · 2 Comments

    Jump to Recipe Print Recipe

    Oh boy! This Cheesy Spinach Mushroom and Onion Casserole is one that will certainly become a staple in your home! It's an incredibly versatile recipe that makes it easy to swap out types of cheese, leave out mushrooms or onions, add in meat or potatoes, etc. The choice is yours.

    a white plate with a square of spinach and cheese casserole

    I first started making this Cheesy Spinach Mushroom Casserole when the boys were little. I was always trying to hide vegetables in my recipes and therefore trick the boys into eating healthy. It worked!

    mushrooms and onions in a saute pan

    How do I know? One of my boys is now a Vegetarian, lol. They all love food and enjoy trying new ingredients and preparations. My twins, who are 27, both love to cook and will jump into the kitchen whenever they can.

    all of the ingredients in a bowl

    This recipe is easy. I wrote this recipe using cheddar cheese only because my youngest child is currently living under our roof and cheddar is his favorite cheese. Covid-19 and the pandemic have sent him home from his senior year at college. I truly didn't think we would ever see any of our kids living at home but here we go. And Jordan is our vegetarian so my cooking has changed ever so slightly. If you would prefer a different type of cheese, feel free to swap it out. I also love a combination of mozzarella and parmesan. I have also used feta, which is delicious, but you will need to decrease the amount you use to cut down on the saltiness.

    all of the ingredients mixed together in a casserole dish

    How to make Cheesy Spinach Mushroom Casserole

    The first step to creating this masterpiece is to saute the mushrooms and onion in butter or olive oil, your choice. I use butter. I also used shitake mushrooms that I had on hand. You don't need to do that. I only had shitake in my fridge!

    Baked spinach casserole

    Cook your frozen spinach for about 4 minutes in the microwave which is enough to warm it up so you can squeeze the water out of it. But, in the picture above, I used cut spinach instead of chopped spinach. Chopped spinach works even better. I just didn't have it in my freezer!

    spinach casserole on a white plate with a fork

    Combine all of the ingredients and bake for about 45 minutes. You want the top to be lightly browned and the cheese to be gooey!

    a white plate with a square of spinach and cheese casserole

    Cheesy Spinach Mushroom Casserole

    Cheesy, gooey, with lots of umame, this casserole is sure to please! Eat it for lunch, dinner (or my favorite...breakfast). This is one veggie that your kids will certainly want to eat.
    Print Pin
    5 from 2 votes
    Course: Side Dish
    Cuisine: American
    Diet: Gluten Free
    Keyword: cheesy spinach and mushroom casserole, cheesy spinach casserole, spinach, spinach and mushroom casserole, spinach casserole
    Prep Time: 15 minutes minutes
    Cook Time: 45 minutes minutes
    Total Time: 1 hour hour
    Servings: 8 people
    Calories: 946kcal
    Author: Gwen

    Ingredients

    • 2 oz frozen spinach 10 oz bag
    • 1 whole onion chopped
    • 5 oz mushrooms chopped
    • 2 tablespoon butter
    • 2 whole eggs
    • 2 cups shredded cheese of choice
    • 1 t salt
    • ½ t pepper
    • 2 t garlic powder

    Instructions

    • Preheat the oven to 375 degrees. Grease a 9x13 casserole dish and set aside. Saute the onions in the butter until soft over medium heat. Add the mushrooms and saute until the mushrooms are just starting to brown. Turn off the heat and set aside. Cook the spinach and then drain the water out by squeezing the spinach. Place the spinach into a bowl. Add the onions and mushrooms to the bowl. Add the rest of the ingredients and combine. Pour the mixture into the greased casserole dish. Bake for 45 minutes to an hour. The top should look lightly brown and the cheese melted.

    Notes

    Choose the cheese of your choice. I used cheddar in the pictures but I also love feta or a combination of mozzarella and parmesan. You can take out the mushrooms, add another veggie, or add a protein. This casserole is very versatile. I also used cut spinach in these pictures and not chopped. Feel free to use chopped spinach. It works even better than cut spinach.

    Nutrition

    Calories: 946kcal | Carbohydrates: 17g | Protein: 58g | Fat: 74g | Saturated Fat: 44g | Polyunsaturated Fat: 3g | Monounsaturated Fat: 21g | Trans Fat: 1g | Cholesterol: 245mg | Sodium: 3966mg | Potassium: 913mg | Fiber: 4g | Sugar: 6g | Vitamin A: 8879IU | Vitamin C: 6mg | Calcium: 1227mg | Iron: 3mg
    Print Pin
    Did you make this recipe?Be sure to follow @asweetthyme on Instagram and tag @asweetthyme. You can also post a photo of your recipe on our Facebook page! I appreciate you soooo much!

    Reader Interactions

    Comments

    1. Anonymous

      August 16, 2023 at 8:23 pm

      5 stars
      X

      Reply
    2. Gwen

      August 23, 2023 at 5:45 pm

      5 stars
      x

      Reply

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    Hi, I'm Gwen! I’m so happy you are here! I started blogging as a way to share my recipes with my family and friends. Sharing recipes, connecting with you, and making friends along the way is a lot of fun!

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