This Lentil Casserole combines lots of wholesome vegetables with hearty lentils and flavorful mushrooms, creamy sauce and cheesy topping.
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When I first made this lentil casserole I liked lentils but had no special love for them. In fact, I pretty much dedicated them towards making soups like this spinach lentil soup and lentil chicken soup.
Since then, I’ve come to appreciate them a little bit more with this lentil bake.
Originally, I only cooked lentils because of their health benefits, not because I wanted to. Now I’m starting to appreciate how versatile they are, especially combined with lots of flavorful veggies and a cheesy topping! A little cheese makes everything better!
And this healthy casserole recipe has ticked off all of the above points.
Ingredients for Lentil Casserole
This healthy lentil casserole recipe is packed with vegetables and plant-based protein.
- Mushrooms: Use brown mushrooms or portobello mushrooms for more flavor. You can use white mushrooms, but they have a milder taste.
- Green lentils: Their earthy, nutty taste adds depth of flavor to the dish and tons of protein! Choose uncooked green lentils and make sure to rinse. Brown lentils would work also.
- Vegetables: Finely chopped onion, celery, and grated carrots are sautéed together to create an aromatic base.
- Oil: Avocado oil or olive oil is needed for frying.
- Organic cream of mushroom soup: My favorite brands are Pacific foods and Simple Truth. If you can’t find organic, look for a brand with no preservatives and artificial flavors.
- Broth or water: Low sodium vegetable broth adds lots of flavor but you can use water if you like.
- Spices and herbs: Garlic powder and dried thyme are the main spices, along with salt and pepper to taste.
- Cheese: I’ll use freshly grated mozzarella cheese or cheddar cheese when I can, the pre-packaged shredded cheeses don’t melt the same.
How to Make Lentil Casserole with Mushrooms
Here’s an overview of how to make lentil casserole with mushrooms. It’s simple, hearty, and makes great leftovers!
A full recipe card is located below.
First, you’ll need to preheat your oven to 375 F and spray a large baking dish with cooking spray.
- Sauté vegetables: Heat a large skillet over medium-high heat, then coat with 2 tablespoons of oil. Sauté onion first for 3 minutes, then add celery and carrots and sauté for 5 more minutes. Transfer veggies to the baking dish. We mix everything in it!
- Sauté mushrooms: Heat the same pan on high heat and add mushrooms. Sauté for 5-7 minutes until slightly browned, stirring occasionally and draining liquid into the baking dish. Then transfer mushrooms to the same dish.
- Pre-cook lentils: Return skillet to low heat, add remaining oil along with thyme and garlic powder. Stir until aromatic, about 30 seconds. Add lentils and cook for 2 minutes, then add broth. Bring to a boil and transfer to the casserole dish, scraping the bits off the bottom of the skillet.
- Bake: Add mushroom soup, salt and pepper to the baking dish and stir to combine. Cover and bake for 30 minutes. Remove from the oven and bake uncovered for an additional 15 minutes. Then sprinkle with cheese and bake until cheese is melted.
- Rest and serve: Cover the lentil bake and let it stand for about 20 minutes. Don’t skip! Your casserole with be much tastier!
Tips for Best Results
Here are my tips for making the perfect vegetarian lentil casserole.
- Always rinse lentils: Rinse lentils under cold water to remove any debris.
- To clean mushrooms: I like to give them a quick rinse with cold water and remove dirt with a knife. They brown just fine, and if done right before cooking they won’t turn slimy. You can also use a damp paper towel to wipe them.
- Tightly cover the baking dish: The dish needs to be tightly covered in order to keep the steam in so the ingredients don’t dry out. If your dish has an oven safe, tight fitting lid you can use it. If not, cover with tinfoil.
- Cook longer or for less amount of time: If you like more firm lentils, cook by 5-10 minutes less. For more soft lentils, cook longer. Also remember that ovens vary.
- Let casserole rest after: My #1 tip! Resting allows the juices to settle, making it easier to serve but more importantly, the taste will be so much better after the spices and flavors sit and mingle.
- Using other dish sizes: I’ve always used my 9×13 baking dish, but a smaller dish deep enough to hold all the ingredients works too.
Feel free to customize and make it your own, here’s a few ideas:
- Using other lentils: Brown lentils are like green lentils making them a great substitute. French lentils and Puy lentils are a variety of green lentils but smaller in size. Red lentils can work in a pinch, but your casserole will come out mushier because they cook faster.
- Add wine: Make it more savory with a splash of red wine or white wine when adding lentils to simmer for 2 minutes.
- If you don’t have cream of mushroom: Make this cream of mushroom substitute or sprinkle 2 tablespoons of cornstarch or 4 tablespoons of flour over sauteed veggies in step 2 and stir. Then add 1/3 cup heavy cream or 1 cup milk, stir, bring to a boil and simmer until thickened. Proceed with the recipe.
- Make it dairy free: Use dairy-free or vegan cheese and follow my above instructions for cream of mushroom soup using a plant-based milk instead of heavy cream.
- Add leafy greens: I like adding spinach, kale or Swiss chard to my casseroles.
- Add protein: Brown some cubed chicken or use leftover Instant Pot shredded chicken. Add cooked ground beef, pork, sausage, ham, or bacon to the mushroom and lentil mixture or keep it vegetarian and add tofu or tempeh.
What to Serve Lentil Bake with?
This delicious lentil casserole is super hearty so you can dig right in or serve it with a simple side salad. A wilted spinach salad or healthy cucumber salad would be perfect. For added crunch, grab a handful of tortilla chips or a slice of crusty bread.
Can I Make It Ahead?
Yes, this recipe is meal prep friendly and can be made ahead as a freezer meal.
1-2 days ahead: Keep casserole mixture in a bowl or in a baking dish covered with plastic wrap and store in the fridge for up to 24 hours. Bring to room temperature for 30 minutes on a counter, then bake as per recipe.
As a freezer meal: Assemble as per recipe, tightly wrap with one layer of plastic then a layer of foil, and freeze for up to 3 months. Thaw in the fridge overnight and bake as per instructions plus 5 minutes.
How to Store
Store: Leftovers can be stored in an airtight container in the refrigerator for up to 3 days.
Freeze: Make sure it is completely cool then freeze in an airtight container for up to 3 months.
No, because of the longer bake time the lentils will be well cooked even without pre-cooking.
Yes, follow the recipe and instead of 2 cups water use only 1/4 cup. Also you might have to add less salt if using store-bought canned lentils.
No. You need unsoaked lentils for this recipe because soaked lentils will skew the liquid ratio and cook time.
No. Once everything is sautéed it becomes a dump-and-go recipe, with no stirring required.
This casserole recipe yields lentils cooked with a bite, not mushy rather al dente. If you like very soft lentils bake longer at your own discretion, I would taste test after an extra 15 minutes. Don’t forget lentils will also soften more during 20 minutes of resting.
More Lentil Recipes to Try
Lentil Casserole with Mushrooms
- 1 large onion finely chopped
- 3 large celery stalks finely chopped
- 2 large carrots coarsely grated
- 3 tablespoons oil for frying
- 1 pound brown mushrooms sliced
- 1 teaspoon garlic powder
- 1/2 teaspoon dried thyme
- 1 1/2 cups green lentils uncooked & rinsed
- 11 ounces can organic cream of mushroom soup I use Pacific Foods or Simple Truth
- 1/4 teaspoon salt
- 1/2 teaspoon ground black pepper
- 2 cups water or low sodium vegetable broth
- 1 cup mozzarella cheese shredded
- Cooking spray
- Preheat oven to 375 degrees F and spray large 9×13 baking dish with cooking spray. Set aside.
- Preheat large skillet on medium heat and swirl 2 tablespoons of oil to coat. Add onion and sauté for 3 minutes, stirring occasionally. Add celery and carrots, sauté for more 5 minutes, stirring occasionally. Transfer to previously prepared baking dish (everything gets mixed here).
- Return skillet to high heat and add mushrooms. Sauté for 5-7 minutes or until a bit browned, draining liquid into the baking dish as necessary (flavourful broth for baking) and stirring occasionally. Transfer mushrooms to the baking dish.
- Return skillet to low heat and add remaining 1 tablespoon of oil, along with thyme and garlic powder. Cook for 30 seconds, stirring constantly. Add lentils and cook for 2 minutes. Add water or broth, bring to a boil and transfer to the baking dish, scraping the bits off the bottom of the skillet.
- Add mushroom soup, salt and ground black. Stir well, cover and bake for 30 minutes. Uncover and bake for another 15 minutes. Then sprinkle with cheese and bake for 5 more minutes or until cheese is melted.
- Remove casserole from the oven, cover and let stand for about 20 minutes (very important – casserole is just tastier this way). Serve hot on its own or over spinach, greens, brown rice or whole grain pasta.
- Store: Refrigerate in an airtight container for up to 3 days.
- Freeze: In an airtight container for up to 3 months.