Combine buttermilk and hot sauce in a bowl. Place chicken in a shallow pan and pour buttermilk mixture over chicken. Cover tightly and marinate in the refrigerator for 2 hours.
Preheat oven to 350 degrees F.
Combine egg substitute and whole-grain mustard in a shallow dish. Combine cereal, Parmesan, and oregano in a second shallow dish.
Remove chicken from marinade and drain excess liquid. Dip chicken pieces, 1 at a time, into the egg mustard mixture and then dredge in the cereal mixture. Place chicken on a wire rack set on top of a baking sheet. Lightly spray the chicken with cooking spray. Bake for 35 minutes or until chicken is fully cooked through and juices run clear when pierced with a knife.