Bring a large pot of salted water to a boil.
Add rotini pasta and cook until al dente, about 8-10 minutes.
Drain the pasta and rinse under cold water to cool.
In a large bowl, combine the cooled pasta with tomatoes, bell peppers, olives, onion, and cucumber.
In a small bowl, whisk together olive oil, red wine vinegar, oregano, salt, and pepper.
Pour the dressing over the pasta and vegetables.
Toss gently to combine all ingredients evenly.
Fold in the feta cheese.
Taste and adjust seasoning if necessary.
Cover and refrigerate for at least 30 minutes before serving.