Wash all vegetables thoroughly and pat dry with paper towels.
Dice the cucumbers into 1/2-inch pieces, leaving the skin on for extra texture and nutrients.
Chop the tomatoes into chunks similar in size to the cucumbers.
Thinly slice the red onion into half-moons. If desired, soak in cold water for 10 minutes to reduce sharpness.
If using, dice the green bell pepper and chop the fresh parsley.
In a large mixing bowl, combine the cucumbers, tomatoes, red onion, and bell pepper if using.
In a small bowl, whisk together olive oil, red wine vinegar, lemon juice (if using), oregano (if using), salt, and pepper.
Pour the dressing over the vegetables and toss gently to combine.
Add most of the crumbled feta cheese and toss once more, very gently.
Transfer to a serving dish and sprinkle the remaining feta cheese on top for the traditional "snow-capped" appearance.
If using parsley, sprinkle on top as garnish.
Serve immediately or refrigerate for 15-20 minutes to allow flavors to meld.
