In a large bowl, combine the green olives, cannellini beans, kidney beans, red onion, cherry tomatoes, and parsley.
In a small bowl, whisk together the olive oil, red wine vinegar, dried oregano, salt, and black pepper.
Pour the dressing over the bean salad and toss to coat evenly.
Refrigerate for at least 30 minutes to allow the flavors to meld.
Serve chilled or at room temperature.
