Heat oil in a large pot over medium heat.
Slice mushrooms and mince garlic; chop carrot, bell pepper, and onion. Add all to hot oil. Cook for 10 minutes stirring frequently. Veggies will become caramelized and fragrant.
Add vinegar and cook for 1 minute, scraping pan to loosen browned bits of veggies.
Add bay leaf, tomatoes, water, lentils, and Italian seasoning. Bring to a boil then reduce to a simmer. Cook approximately 25 minutes until lentils have softened. Stir occasionally as it thickens, adding more water if needed.
Meanwhile, cook pasta as directed on package.
Season lentils with salt and pepper and serve over hot pasta with grapes on the side.