In a large mixing bowl, combine the black beans, kidney beans, and chickpeas.

Add the diced red bell pepper, cucumber, red onion, and parsley to the bowl.

In a small bowl, whisk together the olive oil, red wine vinegar, minced garlic, salt, and black pepper.

Pour the dressing over the bean and vegetable mixture and toss to combine.

Chill in the refrigerator for at least 30 minutes before serving to enhance the flavors.