In a saucepan with salted boiling water, cook the orzo al dente. Drain and cool under cold water. Drain again.
In a large pan, heat a little olive oil on medium heat. Cook the chicken for 7 to 10 minutes while occasionally stirring, until the inside is no longer pink.
Add the Haiku shiitake mushrooms and continue cooking for 1 minute while stirring. Remove from heat and set aside to cool.
In a salad bowl, combine the orzo with the chicken, the shiitake, the chopped peppers and the dressing. Salt and pepper to taste. Garnish with green onions.