Cook pasta according to package directions. Drain in a colander. Rinse with cold water; drain again. Set aside.
In a large bowl toss together the tomatoes, cucumber, green onions, and olives.
Add the pasta and mix to combine.
In a container with an air tight lid (or a bottle), combine the olive oil, lemon juice, basil, the 2 tablespoons oregano, garlic, salt, and pepper.
Drizzle over pasta mixture;
Cover and chill in refrigerator for as least 2 hours or up to 24 hours.