If new events are created in the desktop version of the Outlook Calendar with the "Teams meeting" option already applied, the way to disable this feature is to:
Outlook for Office 365
This should be the default software that the vast majority of people are on as older versions are falling out of their support windows.
- Open Outlook and click the File tab.
- Click Options at the bottom left of the window.
- In the Outlook Options window, select Calendar.
- In the Calendar category, there are various calendar options. In front of Add online meetings to all meetings option, click the button Add Meeting Provider and uncheck the option to Add online meetings to all meetings.
- Click OK to save your changes.
Older versions of Outlook
Warning: This will prevent the creation of teams meetings from Outlook entirely.
- In Outlook, click the "File" tab and then "Options" at the bottom of the menu
- Select the "Add-in" tab at the bottom of the menu to the left
- At the bottom of the pop-up screen there is a "Manage" section that should have a dropdown menu next to it. Make sure it has "COM Add-ins" selected and then click "Go"
- Locate "Microsoft Teams Meeting Add-in for Microsoft Office" in the pop-up screen and uncheck the box next to it, then click "Ok"