Bring a large pot of generously salted water to a rolling boil. Add the rotini and cook until al dente according to package directions. Drain the pasta and rinse under cold running water to stop the cooking and cool it down.

While the pasta cools, slice the Persian cucumbers into half-moons, halve the cherry tomatoes, and thinly slice the red onion.

In a small bowl or jar, whisk together the olive oil, fresh lemon juice, dried oregano, and a pinch of salt and pepper until the dressing is well emulsified.

In a large mixing bowl, combine the cooled pasta, cucumbers, tomatoes, onion, and olives. Pour the dressing over the top and toss well to coat everything evenly. Gently fold in the crumbled feta and chopped parsley. Serve immediately or refrigerate for later.