In a large mixing bowl, combine the sliced cucumbers, tomato chunks, and red onion.
In a small bowl, whisk together the olive oil, lemon juice, minced garlic, parsley, oregano, salt, and pepper until well combined.
Pour about three-quarters of the dressing over the vegetables and toss gently to coat everything evenly.
Add the remaining dressing if needed, tasting as you go to adjust seasoning.
Sprinkle the crumbled feta cheese over the top of the salad.
Let the salad sit at room temperature for about 10 minutes to allow the flavors to meld before serving.