In a small bowl, whisk together the olive oil, lemon juice, Dijon mustard, garlic, oregano, salt, and pepper until well combined.
In a large mixing bowl, combine the chickpeas, cucumber, tomatoes, bell pepper, red onion, feta cheese, and parsley.
Pour the dressing over the chickpea mixture and toss gently until everything is evenly coated.
Serve immediately or refrigerate for 30 minutes to allow the flavors to develop.