In a large mixing bowl, combine the chickpeas, red kidney beans, and black beans.
Add the cherry tomatoes, diced cucumber, sliced red onion, and Kalamata olives.
In a separate small bowl, whisk together the extra virgin olive oil, fresh lemon juice, minced garlic, dried oregano, salt, and black pepper until well combined.
Pour the dressing over the bean mixture and gently toss until everything is evenly coated.
Fold in the crumbled feta cheese and chopped fresh parsley, taking care not to break up the feta too much.
For the best Mediterranean Dense Bean Salad flavor, refrigerate the salad for at least 30 minutes before serving to allow the ingredients to absorb the dressing. Toss lightly before serving and enjoy chilled or at room temperature.