Prepare the baby potatoes by rinsing them under cold water and cutting each potato in half. Set aside.

In a large pot, bring salted water to a boil. Add the halved baby potatoes and cook for 15-20 minutes until tender. Drain and let cool slightly.

In a small bowl, combine olive oil, red wine vinegar, Dijon mustard, salt, and pepper. Whisk until well blended.

In a large mixing bowl, combine baby arugula, cherry tomatoes, red onion, Kalamata olives, and feta cheese. Cut the cooled potatoes into bite-sized pieces and add to the bowl.

Drizzle the dressing over the salad mixture and gently toss to coat. Serve immediately or chill for 30 minutes before serving.