How often does Defender do a quick scan?

Usually I see it run the Quick Scan after doing updates which can include Definitions and just about every time I plug in a USB Thumb drive or access a folder on one of my NAS drives.

Bobby Phoenix said:

I've been trying to find a solid answer on this question, but the web is not much help.

I feel you pain!
The more we use web more boring it gets, the trick isn't in how much time we spend searching but rather in memorizing universal keywords and bookmark good finds all the time!

You can find answer to your in multiple places:
1. GPO (Group Policy Object), for example:
Specify the time for a daily quick scan

This policy setting allows you to specify the time of day at which to perform a daily quick scan. The time value is represented as the number of minutes past midnight (00:00). For example, 120 (0x78) is equivalent to 02:00 AM. By default, this setting is set to a time value of 2:00 AM. The schedule is based on local time on the computer where the scan is executing

This is just one, and there are many more.

now about search engine keyword that finds it, it's called ATP which stands for "Advanced Thread Protection"
You can find many interseting stuff here, including various types of schedules scans and how they work in different editions of Windows:

Main page:
https://docs.microsoft.com/en-us/win...at-protection/

More technical stuff, good to search for details:
https://docs.microsoft.com/en-us/mic...o365-worldwide

https://docs.microsoft.com/en-us/win...virus-features

https://docs.microsoft.com/en-us/win...nder-antivirus

ATP seems to be no longer called ATP, my bookmarks no longer lead me to old finds, but in combination with GPO you can learn all the internals that concern your original question

This is link I missed find in my bookmarks, it accurately describes defender scans and gives GPO locations which describe different scans, defaults are described in GPO and from I recall apply to all editions of OS:

https://docs.microsoft.com/en-us/win...nder-antivirus

You can configure scans with Defender but when Microsoft runs Quick scans outside these configurations is a mystery for a purpose I would assume.