Step 1: Right Click the Google Calendar URL and choose "Copy Link Location".
Step 2: Now in Outlook, choose Tools - Account Settings and click the Internet Calendars tab. Press Ctrl+V to paste the URL that you copied in the previous step. Click Add.
The Internet Calendar is now part of your Outlook Send/Receive group and whenever you press F5, Outlook will synchronize its content with the online Google Calendar. Thanks for subscribing!
Subscribe with Microsoft Outlook (Older Versions)
In older versions of Outlook, right-click this link and click "Save As" to download the ics file. Next, use File/Import Export to import the events to the default Calendar folder. Events are not updated automatically, you'll need to download the ics file and import it again (which will result in duplicates of existing items).