Cook orzo in a large pot of boiling salted water until tender but still firm to bite, stirring occasionally. Drain. Rinse under cold water; drain well. Transfer to medium bowl; let cool.
Whisk vinegar and lemon juice in a small bowl; gradually whisk in oil. Pour dressing over orzo. Mix in remaining ingredients. Season to taste with salt and pepper. This can be made 2 hours ahead. Let stand at room temperature. Stir before serving.
Recipe from Sunset Heirloom Tomato Guide