Bring a large pot of salted water to a boil. Add the green beans and cook for 3-5 minutes until bright green and tender-crisp. Drain and immediately transfer to a bowl of ice water to stop the cooking process. Let cool for 5 minutes, then drain again and pat dry.

In a large bowl, combine the cooled green beans, cherry tomatoes, feta cheese, and red onion.

In a small bowl, whisk together the olive oil, red wine vinegar, Dijon mustard, salt, and pepper until well combined.

Pour the dressing over the salad and toss gently to combine. Adjust seasoning if needed.

Garnish with chopped parsley before serving.