Heat a stockpot over medium heat. Add oil and saute onion, celery, carrot and garlic for 5 minutes or until softened. Stir in rice and saute an additional 3 minutes. Add stock, tomatoes, lentils, parsley, vinegar, Italian seasoning, salt, pepper and bay leaf; bring to a boil.
Reduce the heat and simmer, uncovered, stirring occasionally for 1 hour or until rice is tender. Remove and discard bay leaf. Serve hot.