Vegetarian Spaghetti Casserole

Combine spaghetti, pasta sauce and veggies for an easy yet delicious and sliceable vegetarian casserole! This recipe is great for family dinners and meal prep.

I would like to apologize in advance for waiting so long to share this recipe. This is one of those meals that you’ll want to keep on hand for those moments when you’re craving easy comfort food. If you’re anything like me, that happens pretty often!

I was inspired by spaghetti pie when making this recipe, but the actual product ended up as a casserole. Spaghetti pie usually uses ricotta-coated noodles as a “crust” topped with sauce.

This lighter version uses a delicious yet simple combination of spaghetti & tomato sauce baked in a cast iron dish. I add chopped mushrooms for flavor and that “hidden veggie” component and you can easily blend in other sauteed veggies for extra nutrition.

This kid-friendly recipe is great for family dinners served with a green salad and makes delicious leftovers. I think that you’ll love it!

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Customization

Making spaghetti casserole is as quick and easy as you want it to be. 

Spaghetti noodles: White, whole wheat or even protein pasta will work. Cook the noodles until al dente so that the casserole has some texture.

Pasta sauce: I personally think that homemade pasta sauce is the best part of spaghetti pie, but using a 24-28 ounce jar of store bought pasta sauce is an easy way to cut down on cooking time.

Veggies: Finely diced mushrooms add flavor and nutrition. You can also add finely chopped celery, broccoli, carrots, whatever! Just make sure to saute until most of the water is evaporated out and pour off any excess liquid before adding the tomatoes. Make the veggies “hidden” by blending them into the tomato sauce in a blender.

Pro tip: In this recipe you will salt mushrooms while cooking to draw out the moisture. Wait to salt until after cooking when browning mushrooms.

Mozzarella: Shredded mozzarella acts as “glue” to hold the spaghetti together and is a necessary addition to most casseroles. Make this dish vegan by using an equal amount of vegan shreds instead.

If you’d like to add extra plant-based protein, consider sauteing tempeh or plant-based sausages along with the mushrooms.

Step by step instructions

1. Heat a large 12-inch skillet (I love my Greenpan skillet!) over medium-high heat. Add one tablespoon olive oil. Once hot, add minced garlic, onions and finely chopped mushrooms. Sprinkle with 1/4 teaspoon salt. Saute 6-8 minutes, or until mushrooms are soft. Drain off excess liquid.
2. Add chopped parsley, rosemary, thyme, oregano. Saute another 30 seconds to bloom the herbs. Add extra oil as needed. Add the crushed tomatoes with juices, sugar and black pepper. Bring to a rapid simmer over medium high heat. Reduce to a low simmer over medium-low heat. Simmer for 15 minutes then turn off the heat. Taste for salt.This is what the sauce looks like if want to blend in the veggies.
3. Mix together half of the shredded mozzarella, cooked spaghetti and pasta sauce (image #3). Place in a 12-inch cast iron skillet or baking dish.
4. Sprinkle with remaining shredded mozzarella. Bake at 350F until the cheese is melted and golden, about 20 minutes.

FAQ and Tips

• Cast iron: I use a 12 inch cast iron skillet but you can use a regular casserole dish if you don’t have an oven-proof skillet. Any 9×13 or similarly sized heat-proof baking dish will do.
• Moisture: The less watery your veggies are, the more the dish will hold together. Make sure to salt the mushrooms and onions when you add them to the skillet to draw out extra moisture. Drain off extra moisture before adding tomatoes.
• Storage: Keep refrigerated in a closed container for up to 5 days.

Can I freeze casserole?

Yes! This recipe is great as a freezer meal. It will last in the freezer for up to 3 months.

Let the casserole cool to room temp before covering with foil and freezing. You can also slice the casserole and freeze in individual portions. I like to do this for an easy “freezer dinner”. 

If you like this recipe you’ll love this vegetarian chili mac. Here are a few more of my favorite casseroles:

• Vegetarian Breakfast Casserole
• Quinoa & Black Bean Casserole
• Enchilada Casserole
• Tempeh & Veggie Pasta Bake
• Vegan Squash Casserole

Enjoy!

Print Recipe

5 from 1 vote

Vegetarian Spaghetti Pie Casserole

Combine simple ingredients like spaghetti, pasta sauce and veggies for an easy and delicious dinner! Great for meal prep and kid-friendly.

Prep Time25 mins

Cook Time20 mins

Total Time45 mins

Servings: 6 servings

Author: Cassidy Reeser, RDN, LDN

Ingredients

• 1 tablespoon extra virgin olive oil
• 3 cloves garlic minced
• 8 ounces baby bella mushrooms finely chopped
• 1 small yellow onion finely chopped
• 1/4 teaspoon salt
• 1/4 cup chopped fresh parsley
• 1 tablespoon each chopped fresh rosemary, thyme, oregano see note #1
• 28 ounces crushed tomatoes
• 1/2 teaspoon white sugar
• 1/8 teaspoon black pepper
• 12 ounces whole wheat spaghetti
• 1 and 1/2 cup shredded mozzarella cheese divided

Instructions

• Preheat the oven to 350 degrees F. Lightly butter or oil a 12-inch cast iron skillet or 9×13 casserole dish.
• Heat another large 12-inch skillet over medium-high heat. Add one tablespoon olive oil. Once hot, add minced garlic, finely chopped mushrooms and onion. Add additional veggies here if desired. Sprinkle with 1/4 teaspoon salt. Saute 6-8 minutes, or until mushrooms are soft. Drain off excess liquid.
• Add chopped parsley, rosemary, thyme, oregano. Saute another 30 seconds to bloom the herbs. Add extra oil as needed. Add the crushed tomatoes with juices, sugar and black pepper. Bring to a rapid simmer over medium high heat. Reduce to a low simmer over medium-low heat. Simmer for 15 minutes then turn off the heat. Taste for salt.
• Meanwhile, cook the spaghetti to al dente in well salted water according to package instructions. Once cooked, drain the pasta. Transfer spaghetti to the pasta sauce. Stir in 3/4 cup shredded mozzarella.
• Transfer spaghetti and sauce mixture to the oiled cast iron pan. Top with remaining 3/4 cup of shredded mozzarella.
• Bake at 350F for 20 minutes, or until mozzarella is golden and bubbling. Remove from the oven and let rest 5 minutes before slicing to serve. Enjoy!

Notes

1. Fresh herbs: Rosemary, oregano and thyme can each be replaced with 1 teaspoon dry herbs.
2. Extra veggies: Add carrots, squash or even peas for extra veggies. You can blend the pasta sauce after simmering if you prefer a “hidden veggie” sauce. Be careful if blending as it will be very hot.
3. Store refrigerated in a closed container for up to 5 days. To freeze, cover the cooled casserole with foil and freeze for up to 3 months.

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Serving: 1sliceCalories: 356kcalCarbohydrates: 55gProtein: 18gFat: 10gSaturated Fat: 4gCholesterol: 22mgSodium: 454mgPotassium: 706mgFiber: 3gSugar: 7gVitamin A: 474IUVitamin C: 13mgCalcium: 219mgIron: 4mg