Preheat oven to 375 degrees.
Season chicken breast halves with salt and pepper then place them on a baking sheet coated with the olive oil. Roast for 25 minutes or until internal temperature registers 165 degrees and juices run clear. Set aside to cool.
In a medium bowl, toss together next 9 ingredients (onion through yogurt). Cube cooled chicken and add to onion/yogurt mixture; toss well to blend. Refrigerate until chilled.
Place a lettuce leaf on each dinner plate; fill each with an equal portion of chicken salad.