Cook the orzo pasta according to package instructions until al dente. Drain and rinse under cold water to stop the cooking process. Set aside.
In a large mixing bowl, combine the drained tuna, cherry tomatoes, cucumber, red onion, black olives, parsley, and feta cheese.
In a small bowl, whisk together the olive oil, red wine vinegar, dried oregano, salt, and pepper.
Add the cooked orzo to the mixing bowl with the other ingredients. Pour the dressing over the salad and gently toss until everything is well combined.
Taste and adjust seasoning if necessary. For best flavor, let the salad chill in the refrigerator for at least 30 minutes before serving.