In a large mixing bowl, combine the cannellini beans, grape tomatoes, zucchini, yellow bell pepper, red onion, and basil.
In a separate bowl, whisk together the olive oil, balsamic vinegar, whole grain mustard, sea salt, and black pepper until smooth.
Drizzle the dressing over the bean and vegetable mixture and gently fold everything together until evenly coated.
Allow the salad to rest for about 20 minutes at room temperature to enhance the flavors.
For a more refreshing taste, refrigerate for 30 minutes before serving.
Enjoy the salad chilled or at room temperature.