Preheat oven to 350 degrees. Spread pecans in a single layer on a rimmed baking sheet. Toast in oven until fragrant, stirring occasionally, about 10 minutes. Remove from pan; let cool completely.
Pull chicken from the bone; discard bones, and cut meat into 3/4-inch pieces. Transfer to a medium bowl; add scallions, celery, apples, raisins, and oregano. Season with salt and pepper. Add dressing; toss to combine. Chill, covered, until ready to serve.