With my O-1 visa, how long can I stay in the US after my employer fired me ?

There is no period of time allowed an individual to remain in the States under an O-1 visa after being fired by an employer. That being said, U.S.C.I.S. tries to be reasonable in those situations, and in the H-1B context, one of its supervisors at the Vermont service Center informed the New York AILA chapter some time ago that U.S.C.I.S. would generally accept new applications submitted within 30 days in those type of situations, but that it was in the individual officer's discretion. Your spouse is dependent upon you and would enjoy no better rights than you to remain in the States.Due to the limitations of the Lawyers.com Forums, Alan Lee, Esq.'s (the "Firm") participation in responding to questions posted herein does not constitute legal advice, nor legal representation of the person or entity posting a question. No Attorney/Client relationship is or shall be construed to be created hereby. The information provided herein by the Firm is general, and requires that the poster obtain specific legal advice from an attorney. The poster shall not rely upon the information provided herein as legal advice nor as the basis for making any decisions of legal consequence.  

There is no grace period.  Once your employer terminates your employment, you would have to leave the US and get a new visa to return.