>I have the same query on two servers. They are configured the same against the same database with the same set of indexes. All the indexes in regards to the execution plan have been re-indexed. However, one server is showing the execution plan in parallelism mode and the other server not. What is causing this?

Take a look at this blog post http://blogs.msdn.com/b/psssql/archive/2013/09/27/how-it-works-maximizing-max-degree-of-parallelism-maxdop.aspx and try querying MAXDOP property on both servers.