Preheat an oven to 350 degrees F (175 degrees C). Spray a baking sheet with cooking spray.
Season the chicken pieces with salt and pepper to taste and place skin-side-up onto the prepared baking sheet. Bake in the preheated oven for 20 minutes.
While the chicken is baking, stir together the plum jam, 1 1/2 teaspoons pepper, ginger, and horseradish in a small bowl. After the chicken has baked 20 minutes, brush with the plum glaze and return to the oven.
Continue baking until no longer pink at the bone and the juices run clear, 20 to 30 minutes more. An instant-read thermometer inserted near the bone should read 165 degrees F (74 degrees C).