Add the olive oil to a large, deep skillet or a medium pot. Warm over medium heat.
If using, add the sweet Italian sausage. Cook for 6 to 8 minutes, or until mostly browned, breaking it up with a wooden spoon as it cooks.
Add the baby potatoes, zucchini, green beans, sweet bell pepper, marinara sauce, and 1 cup of water or broth. It’s okay if you measure roughly and have a little more or less of any one ingredient.
Bring the mixture to a simmer. Reduce the heat to medium-low and cover the pot.
Cook for about 25 to 35 minutes or until all the vegetables are soft, stirring occasionally.
Once the vegetables are soft, season to taste with salt and pepper.
Serve warm with a sprinkle of grated Parmesan cheese and fresh basil, if desired.
