In a large mixing bowl, combine the beans, artichoke hearts, onion, cucumber, parsley, (and tomato, olives and basil, if using).
In a small bowl, whisk together the olive oil, lemon juice, mustard, garlic, oregano, salt, and pepper until emulsified.
Pour the dressing over the salad and toss gently to combine.
Chill to let flavors meld, or serve immediately.