Bring a large pot of generously salted water to a boil. Add the macaroni and cook according to package directions.

Drain and rinse under cold water.

Meanwhile, in a large bowl, combine mayonnaise, vinegar, diced tomatoes (and their juice), olives, red onion, garlic powder, oregano, salt, and pepper. Mix well.

When the pasta is done, mix it into the dressing and serve immediately at room temperature or chilled.