Begin by rinsing and draining the chickpeas and black beans under cold water to remove excess sodium. Transfer to a large mixing bowl.

In a separate bowl, whisk together the olive oil, red wine vinegar, oregano, salt, and black pepper until well combined.

Pour the dressing over the beans, tossing gently to coat.

Fold in the sliced red onion, crumbled feta, and chopped parsley.

Cover and chill for at least 30 minutes before serving.