Drain and rinse the chickpeas, kidney beans, and black beans thoroughly.
Add all three beans to a large mixing bowl.
Stir in the cherry tomatoes, cucumber, red onion, and Kalamata olives.
In a separate small bowl, whisk together olive oil, lemon juice, garlic, oregano, salt, and black pepper until well combined.
Pour the dressing over the salad ingredients.
Toss gently until everything is evenly coated.
Fold in the crumbled feta cheese and chopped parsley.
Toss lightly once more to avoid breaking the feta.
Serve immediately or refrigerate for about 30 minutes to allow the flavors to blend beautifully.