Cover a baking sheet with aluminum foil and coat with cooking spray. Lay mushrooms in one layer on the pan and coat with cooking spray.
Bake mushrooms for 20 minutes and let cool. Chop mushrooms and mix together with orzo, tomato, vinaigrette, dill, and chives. Sprinkle with salt and pepper and spoon mixture into lettuce leaves. Wrap the lettuce around the filling to make lettuce wraps.