Trim chicken breasts then place in a gallon-sized resealable bag. Mix buttermilk, salt and pepper together then pour over chicken breasts. Seal bag then move chicken around to coat completely in buttermilk. Allow chicken to marinate in the buttermilk mixture for at least 30 minutes and up to 8 hours.

Preheat oven to 400 degrees. Crush entire package of croutons into fine crumbs by hand or by pulsing in a food processor then pour onto a large plate or shallow dish (like a pie dish). Spray a 9" x 13" casserole dish with cooking spray.

Remove chicken from marinade then dredge each breast in crouton crumbs to coat completely. Place in baking dish. Discard excess marinade.

Bake 25–35 minutes depending on thickness, until thickest part of chicken has cooked through. Remove from oven and allow chicken to rest 2 minutes before serving.