This cozy and super delicious Slow Cooker Lentil Soup is an easy vegetarian recipe filled with hearty lentils, vegetables, flavorful herbs, and spinach.
Today I’m sharing a wonderful, comforting vegetarian soup that I’ve been making regularly for meatless Monday. Sometimes, all I’m craving is a bowl full of veggies and nourishment, and this cozy lentil soup with hearty potatoes delivers.
You can make this recipe in a crock pot or in a slow cooker, whichever one you have handy. This makes it perfect to set and forget, only to return to a comforting pot of homemade soup brimming with flavor.
Then it’s just a matter of finishing it off with some greens, and a sprinkle of parmesan cheese, and there you have it! Delicious and satisfying lentil soup, made without lifting a finger (well, barely).
What Are the Best Lentils for Soup?
Lentils come in many different colors and sizes, but just about any type of lentil can be used to make lentil soup. For this slow cooker recipe, I use green lentils, as they hold their shape over low and slow heat. Brown lentils are another good option.
You can also make red lentil soup, just note that red lentils cook faster and may call for a shorter cooking time.
Ingredients You’ll Need
Lentils don’t have to be boring, and this soup proves it! My lentil soup recipe is choc full of filling ingredients, from tender veggies to russet and sweet potatoes, to spinach. Below is a quick summary of the ingredients, with the full details available in the recipe card.
Potatoes: I use a combination of sweet potatoes and russet potatoes. Make sure you’re using a type of boiling potato that holds up well in soups.
Carrots and Onion: Diced veggies, along with a bit of minced garlic, bring an aromatic flavor to the soup.
Herbs and Spices: Aside from your obvious salt and pepper, this recipe calls for basil, oregano, dried thyme, and red pepper flakes.
Lentils: I use green lentils for my soup. As mentioned, you can use pretty much any variety or combination of uncooked lentils you prefer. You can also use split peas.
Vegetable Broth: The better the quality of your broth, the better the soup will taste. So choose a good quality vegetable broth or stock, or make your own. If you’re not making a vegetarian soup, you can use chicken stock instead (try my recipe for Homemade Chicken Stock).
Olive Oil: Like your stock, make sure the olive oil you’re using is high-quality.
Spinach and Parsley: I love adding a sprinkle of baby spinach and chopped fresh parsley to the soup right at the end, for a pop of green. Kale can be used in place of spinach, just remove the stems.
Red Wine Vinegar: Also added at the end, to brighten the flavors.
Parmesan Cheese: This is optional, but it does make a yummy garnish. Omit parmesan if you’re making a vegan lentil soup.
Do Lentils Need to Be Soaked Before Making Soup?
Generally speaking, lentils don’t need to be soaked before they’re added to most soup recipes. This is because they tend to cook right in the broth. You don’t need to soak the green lentils at all for this slow cooker soup. The lentils soften up perfectly while inside the pot.
How to Make Lentil Soup in the Slow Cooker
Who doesn’t love a dump-and-go crock pot recipe? Once this soup is in the slow cooker, your hands are free to make a side of Perfect Garlic Knots or even French Bread for dunking. Don’t forget to check out further down in this post for easy ways to turn this soup into a meal!
Combine and Cook: Add the soup ingredients, seasonings, and broth to your slow cooker, and set it to cook on high. Then, walk away.
Blend: After 4-5 hours, the veggies and lentils should be tender. Scoop out 4 cups of the soup and add them to your food processor, then blend with olive oil. This is the secret to an extra-luxurious, silky lentil soup! Add the smooth puree back into the slow cooker.
Finish: Adjust the soup’s seasoning to taste, then stir in the spinach leaves and chopped parsley. Replace the lid and cook on low for another 15 minutes or so, just enough time to wilt the spinach.
Serve: Finally, stir in the red vinegar and give your lentil soup a final stir. It’s ready to serve! I love to top my bowls with freshly grated parmesan. See below for more serving ideas.
Can I Make This Recipe On the Stovetop Instead?
Certainly. No slow cooker? Or maybe you’re craving this hearty soup in a hurry (understandable). No problemo. Here’s how to easily make this lentil soup on the stovetop:
Add the soup ingredients to a large pot on the stovetop, leaving out the spinach, parsley, and vinegar for now.
Bring the soup to a boil, then cover and simmer for about 25 minutes, or until the lentils and potatoes are tender. Blend a portion of the soup as directed in the recipe.
Stir in the spinach and parsley, and simmer on low until the spinach wilts. Finish with red vinegar as usual, and serve!
Tips and Variation Ideas
Here are my tips for making the best lentil soup, as well as some simple ways to change up the ingredients:
Try not to overcook the lentils. The flavors will still be delicious, but overcooked lentils can become mushy, and your soup might lose some of its texture.
Use an immersion blender to blend the soup if you have one. You can puree the lentils right in the bowl of your slow cooker!
When blending the hot soup, make sure that your blender or food processor has an opening for the steam to escape. Otherwise hot soup + sealed blender = soup explosion all over your kitchen. Also, remember to not fill the blender more than halfway full.
Add more veggies. Try adding mushrooms, or canned or fresh tomatoes.
Make it meaty. If you’re after more protein, baked ham and cooked bacon go really nicely in lentil soup. Or, make sausage lentil soup with chopped cooked pork sausage.
Serving Suggestions
This soup is pretty substantial, so a bowl (or two) is often enough to fill us up! In case you wanted to turn it into a meal, here are some tasty side dish recipes to try:
Storing and Reheating Leftover Soup
Store any leftover slow cooker lentil soup airtight in the fridge for up to 5 days. Reheat the soup either in the microwave in increments or on the stovetop. If you feel that the soup has thickened, stir in additional water or broth.
Can I Freeze Lentil Soup?
Yes! This homemade lentil soup can be frozen for up to 3 months. Let the soup cool completely, then transfer it to an airtight, freezer-safe container to store. Thaw the soup overnight in the fridge, then reheat.
This satisfying Slow Cooker Lentil Soup is a comforting vegetarian soup recipe made with tender lentils, hearty vegetables, herbs, and spinach in a cozy broth.
2 cups peeled and cubed sweet potatoes
2 cups peeled and cubed russet potatoes
2 cups peeled and sliced carrots
1 small yellow onion, diced
6 cloves garlic, minced
1 1/2 teaspoon kosher salt
1 teaspoon ground black pepper
1 teaspoon basil
1 teaspoon oregano
1/2 teaspoon dried thyme
1/2 teaspoon red pepper flakes
1 3/4 cups green lentils (or a mix of lentils and split peas)
8 cups vegetable broth
1/3 cup quality olive oil
3 cups baby spinach (or kale stems removed)
1 cup fresh parsley, roughly chopped
2 tablespoons red wine vinegar
Optional – Parmesan cheese
Add sweet potatoes, potatoes, carrots, onion, garlic, salt, pepper, basil, oregano, thyme, red pepper flakes, lentils, and broth into a large slow cooker. Cook on high for 4 – 5 hours, until the lentils and vegetables are soft.
Transfer 4 cups of the soup to a food processor or blender with the olive oil and pulse until smooth. Add this back into the slow cooker and stir to combine. Adjust seasoning now if necessary.
Add in the spinach and parsley and stir. Place the lid back on the slow cooker and adjust to low. Cook for an additional 15 minutes, to wilt the spinach (or kale).
Add in the vinegar and stir. Serve warm with Parmesan cheese on top if desired.
