How can I file taxes with my new foreign spouse who doesn't have a social security number

I am an American citizen and got married to a foreign spouse in November 2015. My wife came on a K-1 fiancee visa, which has since expired and we are waiting on her green card application to be processed by the department of homeland security. Until we get her green card, she can't get a social security number, which I need to do our taxes. What are my best options for filing my 2015 tax return? We are both living in the United States now.