Hearty Vegan Mushroom Barley Soup (Slow Cooker)

Soups

March 21, 2026

There’s nothing quite like coming home to the rich, savory aroma of a soup that’s been simmering away all day. This Slow Cooker Mushroom Barley Soup is the ultimate ‘set it and forget it’ meal. It’s packed with earthy mushrooms, wholesome barley, and a medley of vegetables and herbs that meld together into a deeply flavorful and satisfying dish. It’s a hug in a bowl, completely vegan, and ridiculously easy to make. Perfect for chilly evenings, busy weekdays, or whenever you need a simple, nourishing meal.

Ingredients

• 8 ounces / 225 g fresh portobello mushrooms, cut into thirds and sliced
• 8 ounces / 225 g fresh button or cremini mushrooms, sliced
• 1 14.5-ounce / 411 g can diced tomatoes, undrained
• 1 cup / 120 g sliced carrots (about 2 medium)
• 1 cup / 150 g chopped onion (about 1 large)
• 1/2 cup / 100 g pearl barley, rinsed
• 2 tablespoons / 30 ml tomato paste
• 1 tablespoon / 15 ml balsamic vinegar
• 3 cloves garlic, minced
• 1 teaspoon / 5 ml dried marjoram, crushed
• 1/2 teaspoon / 2.5 ml salt
• 1/2 teaspoon / 2.5 ml paprika
• 42 ounces / 1.25 L vegetable broth (3 14-ounce cans)
• For Garnish (Optional)
• Vegan Parmesan-style cheese, shredded
• Fresh Italian (flat-leaf) parsley, snipped

Instructions

1. In the basin of a 4- to 5-quart slow cooker, combine the portobello mushrooms, button mushrooms, undrained diced tomatoes, carrots, onion, barley, tomato paste, balsamic vinegar, garlic, marjoram, salt, and paprika. Pour the vegetable broth over the mixture and stir to combine.
2. Cover the slow cooker and cook on the low-heat setting for 8 to 10 hours or on the high-heat setting for 4 to 5 hours, until the barley and vegetables are tender.
3. Ladle the soup into bowls. Garnish each serving with a sprinkle of vegan Parmesan-style cheese and/or fresh parsley, if desired.

Nutritional Information

• PER SERVING (approximate, without garnish): 135 cal., 1 g total fat (0 g sat. fat), 0 mg chol., 1,192 mg sodium, 28 g carb., 6 g fiber, 6 g pro.

Pro Tips

• For a deeper flavor, sauté the onions, garlic, and mushrooms in a skillet with a touch of olive oil for 5-7 minutes until softened and lightly browned before adding them to the slow cooker.
• Feel free to use any combination of your favorite mushrooms. Cremini, shiitake, or oyster mushrooms would all be delicious additions and add more complex flavor.
• To boost the umami flavor, add 1 tablespoon of soy sauce or tamari along with the vegetable broth.
• This soup freezes beautifully. Allow it to cool completely, then store it in airtight containers in the freezer for up to 3 months. The barley will absorb more liquid upon reheating, so you may need to add a splash of broth.

FAQ

Q: How can I add more protein to this vegetarian mushroom barley soup
A: To boost the protein content, consider adding a can of rinsed and drained chickpeas or white beans (like cannellini or Great Northern) during the last 30 minutes of cooking. You could also stir in some cooked lentils or top the finished soup with toasted pumpkin seeds for an extra protein punch.

Q: Can I make this mushroom barley soup gluten-free
A: Yes, you can easily make this soup gluten-free. Simply substitute the pearl barley with an equal amount of a gluten-free grain like brown rice, quinoa, or certified gluten-free steel-cut oats. Note that cooking times may vary slightly depending on the grain you choose, so check for tenderness.

Q: How do I get a rich beefy flavor without using meat
A: This recipe builds a deep, savory flavor using several vegan-friendly umami sources. The combination of portobello mushrooms, tomato paste, and balsamic vinegar creates a rich base. For an even deeper, ‘beefier’ taste, you can add 1 tablespoon of soy sauce or tamari, a teaspoon of miso paste, or use a high-quality mushroom-based vegetable broth as suggested in the pro tips.

Q: Does this vegan barley soup store well for meal prep
A: Absolutely. This soup is perfect for meal prep. It can be stored in an airtight container in the refrigerator for up to 5 days. It also freezes beautifully for up to 3 months. Be aware that the barley will continue to absorb liquid as it sits, so you may need to add a splash of vegetable broth or water when reheating to reach your desired consistency.

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