Bring a large pot of salted water to a boil. Cook pasta according to package directions until al dente, about 10 minutes. Drain and rinse under cold water.

While pasta cooks, halve the tomatoes, dice the cucumber and bell pepper, slice the onion, and chop the parsley. Place them in a large bowl with the olives.

In a jar or bowl, combine olive oil, vinegar, lemon juice, Dijon, garlic, oregano, salt, and pepper. Shake or whisk until emulsified.

Add the cooled pasta to the vegetables. Pour the dressing over the top and toss well to coat.

Cover and refrigerate at least 30 minutes. Toss again before serving and garnish with extra parsley. Serve cold or at room temperature.