@johnpowell. Thanks. I looked around and found every keyboard shortcut but that one, apparently. Where should I have looked or how should I have written my query?
I’m not really sure. I have just always known it. It was pretty essential back in the days before OS X. It also works in the Finder, which is where I use it most.
To find lists of shortcuts on the computer itself:
Click on the desktop.
Go to the “Help” option on the menu bar.
Type in the search box “Shortcuts” and click the first option “Keyboard and other shortcuts”.
Voila! You have several choices from here. Choose System Basics > Shortcuts for windows to find the Command+Q.