In a large bowl, combine the diced cucumbers, halved cherry tomatoes, sliced red onion, and chopped parsley.
In a small bowl, whisk together the olive oil, red wine vinegar, garlic powder, salt, black pepper, and dried oregano until well combined.
Pour the dressing over the salad ingredients and toss gently to coat everything evenly.
Let the salad sit for at least 15 minutes to allow the flavors to meld. For best results, refrigerate for 30 minutes before serving.
Serve chilled or at room temperature.