In a large mixing bowl, combine the diced cucumbers, red bell pepper, yellow bell pepper, cherry tomatoes, red onion, and parsley.
In a small bowl, whisk together the olive oil, red wine vinegar, garlic powder, salt, black pepper, dried oregano, and lemon juice until well combined.
Pour the dressing over the salad and toss gently to coat all the vegetables 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.