Place chicken and buttermilk in a large bowl or zip-top plastic bag, turning chicken to coat all sides. Cover or seal, and chill 8 hours. Drain chicken, discarding buttermilk.
Combine flour, poultry seasoning, and lemon pepper in a bowl. Set aside.
Whisk egg whites in a medium bowl until frothy.
Dredge chicken in flour mixture, dip in egg whites; gently press chicken in crushed cereal.
Arrange chicken on a wire rack coated with cooking spray in an aluminum foil-lined 15- x 10-inch jellyroll pan. (Do not overlap chicken.) Lightly coat chicken evenly on both sides with cooking spray.
Bake at 375° for 45 minutes or until chicken is done.