Add the diced onion, carrots, celery, and garlic to the slow cooker.
Stir in the rinsed lentils, crushed tomatoes, vegetable broth, and red wine.
Add the bay leaves, dried thyme, salt, and black pepper. Stir everything to combine.
Cover and cook on low for 7 to 8 hours or on high for 4 hours, until the lentils are tender but still hold their shape.
Remove the bay leaves, taste, and adjust salt or pepper if needed.
Ladle into bowls and sprinkle with the chopped parsley before serving.