Slice cucumbers into ¼-inch thick rounds. If using regular cucumbers with larger seeds, consider removing the seeds by cutting the cucumber in half lengthwise and scraping the seeds out with a spoon.
Halve the cherry tomatoes or dice larger tomatoes into bite-sized pieces. Slice the red onion as thinly as possible. Pro tip: If you find raw onions too strong, soak the slices in cold water for 10 minutes before adding them to your salad.
In a large bowl, gently toss together the cucumbers, tomatoes, red onion, mint, and parsley.
Whisk together olive oil, lemon juice, oregano, salt, and pepper in a small bowl.
Pour the dressing over the vegetable mixture and toss gently. Add the crumbled feta and give it one more delicate toss. For best results, refrigerate for 30 minutes before serving to allow the flavors to meld together.