In a large bowl, combine chickpeas, red onion, cherry tomatoes, cucumber, and parsley.
In a small bowl, whisk together olive oil, lemon juice, Dijon mustard, salt, and pepper.
Drizzle the dressing over the salad and toss to coat evenly.
Gently fold in the crumbled feta cheese.
Serve immediately or refrigerate for at least 30 minutes for flavors to meld.