Heat olive oil in a skillet over medium heat. Add the diced onion and sauté for 3-4 minutes until softened.

Add the minced garlic to the skillet and cook for 1 minute until fragrant. Transfer the onion and garlic mixture to the slow cooker.

Add the carrots, celery, potatoes, zucchini, green beans, frozen corn, and frozen peas to the slow cooker.

Pour in the diced tomatoes (with their juices) and the vegetable broth.

Stir in the dried thyme, dried basil, and add the bay leaf. Season with salt and black pepper to taste.

Cover the slow cooker and cook on low for 6-8 hours or on high for 3-4 hours, until the vegetables are tender.

Remove the bay leaf before serving. Taste and adjust seasoning if needed.

Ladle the soup into bowls and garnish with freshly chopped parsley, if desired.