Before you can use the Large Gallery View in a Teams meeting, or any of the new features really, you need to enable the “new meeting experience”
Click on the ‘Profile’ icon on the Title Bar and select ‘Settings’ from the menu.
In the ‘General’ settings, go to the ‘Turn on new meeting experience’ option and click on the checkbox next to it to enable it. Then, restart your Microsoft Teams as the new features won’t show until you restart the desktop app.
If you couldn’t find the setting mentioned above, first make sure that your desktop client is on the latest version. Go to the ‘Profile’ icon and click on ‘Check for Updates’ from the menu.
Microsoft Teams will scan if there is an update available and install it
How to Use the Large Gallery View in Teams Meetings
When there are more than 10 participants in a meeting, only then you will get the ‘Large Gallery’ option. To enable it, click on the ‘More actions’ icon (three dots) on the meeting toolbar in an ongoing meeting.
Now, click on the ‘Large Gallery’ option from the menu to enable it.
The large gallery view will display the videos of 49 participants in a 7×7 grid.