Apple - How to view Software Update history?

It can be found in an easy to read format using the system information app:

System Information.app > Software > Installations

System information can be found in /Applications/Utilities/System Information.app or via Spotlight.

It is not easy to read, but it appears to be up to date on my machine. You can find the Install history in: /Library/Receipts/InstallHistory.plist

Wouldn't it be nice it this were listed in the Update tab of the Mac App Store?

/private/var/log/install.log

/Library/Receipts/InstallHistory.plist