Vegan Zucchini and Bean Casserole

Preheat the oven to 400 degrees F (200 degrees C).

Heat oil in a large skillet over medium-high heat. Add zucchini, onion, and bell pepper and saute until crisp-tender, about 5 minutes. Add green beans, sausage, and garlic and saute for another 3 to 4 minutes. Stir in cannellini beans, marinara sauce, basil, and mustard; bring to a boil. Spoon into a shallow 2-quart baking dish.

Bake in the preheated oven until vegetables are tender and casserole is heated through, about 20 minutes. Serve warm.