Bring a pot of salted water to a boil. Add the green beans and cook for 2-3 minutes, until crisp-tender. Drain and transfer to a bowl of ice water to cool. Drain again and set aside.
In the same pot of boiling water, add the baby potatoes and cook for 8-10 minutes, until fork-tender. Drain and set aside.
In a small bowl, whisk together the olive oil, red wine vinegar, Dijon mustard, salt, and pepper to make the dressing.
In a large salad bowl, combine the green beans, potatoes, tuna, eggs, olives, cherry tomatoes, red onion, and parsley. Drizzle with the dressing and toss to coat.
Serve the salad chilled and enjoy!