Configuring preferences and options in Outlook.com
Hi, Nick Hawks
The published Outlook calendar link only covers a limited window of dates, so Google can't show events that aren't in the feed in the first place.
Here are some suggestions you can try:
First, check the feed itself. Sign in to Outlook on the web, go to Settings > Calendar > Shared calendars, and copy the ICS link (not the HTML one). Paste it into your browser to download the file, then open it in Notepad and look for an event that's more than six months out. If it's not in the file, Google can't show it.
If those events are missing, it is suggested that you skip the link and use an app that connects straight to your Outlook account. For example, the Events Calendar app in the Wix App Market can sync Outlook events directly, so your website doesn't depend on Google's subscription.
As a stopgap, you can upload the downloaded .ics file to Google Calendar (Settings > Import & export). It will show the far-out events, but it's a one-time snapshot, so you'd have to repeat it when things change.