Bring a large pot of water to a boil. Cook orzo in the boiling water, stirring occasionally until tender yet firm to the bite, about 11 minutes. Drain and rinse with cold water.

Combine orzo, chicken, tomatoes, red onion, basil, and oregano in a large bowl.

Whisk vinegar, oil, salt, and pepper in a separate bowl. Drizzle over the pasta mixture. Toss to coat. Sprinkle with olives and feta cheese.