You can subscribe to ISS calendar posted on Google Calendar. An Internet Calendar Subscription keeps your Outlook copy of your Google Calendar updated. Outlook periodically checks the Google Calendar for updates, and if any are found, they are downloaded to the calendar copy in Outlook.

    1. Select this Internet Web address , and then press CTRL+C to copy the selected text to the Windows clipboard.
    http://www.google.com/calendar/ical/iss.utep%40gmail.com/public/basic.ics

      Note: DO NOT CLICK THE LINK. If you click the link, the calendar will be opened in Outlook as a Calendar Snapshot which is not updated.

   2. In Outlook, on the Tools menu, click Account Settings.
   3. On the Internet Calendars tab, click New.
   4. Paste the Internet Web address you copied in step 1, by pressing CTRL+V.
   5. Click Add.
   6. In the Folder Name box, type the name of the calendar as you want it to appear in Outlook, and then click OK.


Source: Transfer calendars between Outlook and Google Calendar.