In a large bowl, combine the cooked quinoa and cooked chicken breast.
Add the diced cucumbers, tomatoes, and crumbled feta.
In a small bowl, whisk together olive oil, balsamic vinegar, black pepper, and salt.
Pour the dressing over the salad and toss until everything is well coated.
Taste and adjust seasoning if needed.
Serve immediately or chill in the fridge for 2 hours for best flavor.