The menu, including breaded chicken and vegetable nuggets, has been set out by the council for schools throughout the county, prompting uproar from politicians and parents.
County councillor Joy Jones set up a petition calling for a traditional dinner to be served, and that has been signed by over 5,500 people.
She has been backed by Montgomeryshire AM Russell George, who has sent a letter on the matter to council leader Rosemarie Harris.
Mr George said: "I'm calling on Powys County Council to re-instate the traditional Christmas dinner on the school menu.
"A Margherita pizza finger and a vegetable nugget just doesn't cut the mustard I'm afraid. Turkey and all the trimmings and a suitable vegetarian alternative should be put back on the menu this year.
"We all know that Powys County Council is under financial pressure and that the Welsh Government must do more to adequately fund the county council's services, but I question whether spending a little extra on providing a traditional school Christmas dinner is going to break the bank.
"Montgomeryshire's 'Tiny Tims' look forward to their traditional Christmas dinner at the end of term and this kind of action does little to save much money but does a lot to make the county council look like Ebenezer Scrooge before he came to his senses.
"I sincerely hope that they will reconsider this decision at the earliest opportunity and spread some Christmas cheer among schools across Montgomeryshire."
In his letter, Mr George has stated that it goes against the council's aims on its website, to "encourage healthier eating through our menu choices and we avoid harmful additives".