Extend a recurring meeting in Outlook

In classic Outlook, on the calendar grid, select an instance of the recurring meeting. 

On the ribbon, select Open > Open Series.

In the header of the meeting, select Edit Recurrence. 

Adjust the End by date or change the No end date option as needed.

Select OK, and then select Send Update to save the changes and notify attendees.

In new Outlook, locate an instance of the recurring item on the calendar grid; double-click it to open it.

Open an instance of the recurring meeting by double-clicking it on your calendar.

Below the toolbar, select Edit series or Edit this and all following events.

Next to the end date, select the  recurrence option, then choose a recurrence pattern: Daily, Weekly, Monthly, or Yearly.

In the Repeat dialog, choose the recurrent pattern you want. You can select the end date and then change it, or you can remove it entirely in new Outlook​​​​​​​. 

Select Save, and then select Send to notify the attendees.