Heat oil in a large saucepan over medium-high heat. Add carrots, zucchini, celery and onion. Cook, stirring occasionally, for 10 minutes or until vegetables begin to soften.
Add tomatoes and stock to pan. Cover and bring to the boil. Reduce heat to medium-low. Simmer, partially covered, for 15 minutes or until vegetables are soft.
Add lentils to soup. Cook for 5 minutes or until heated through. Ladle soup into bowls. Sprinkle with parsley and squeeze lemon juice. Season with freshly ground black pepper. Serve with lemon wedges and bread rolls.