Preheat oven 400° and prepare an 8x8 casserole dish by spraying with Pam cooking spray.
In a large mixing bowl, combine frozen mixed vegetables, chopped chicken breast, poultry seasoning, salt, pepper, and cream of mushroom soup. Mix well. Pour in casserole dish.
In a medium bowl, combine Bisquick, skim milk, and egg substitute. Mix well. Pour over top of chicken mixture.
Bake in preheated oven 30 minutes, or until crust is golden.