Place the chicken breasts in the bottom of your slow cooker. Pour the Italian dressing over the chicken so it is coated. Cover and cook on low for about 4 to 5 hours or until the chicken is tender and can be easily shredded.

Once the chicken is cooked, let it cool slightly. Shred or chop the chicken and keep it stored in the slow cooker juices until you are ready to make the salad. This helps keep the chicken moist and flavorful.

When you are ready to assemble the salad, place the shredded chicken in a large bowl. Add the grapes and chopped apple. Stir in the pistachios for crunch. Mix in the mayonnaise or Greek yogurt until everything is combined. Season with salt and pepper to taste.

Chill the chicken salad in the refrigerator before serving. This gives the flavors a chance to come together.