Outlook for the Web offers a way to mask the attendee list in a calendar invite. This will prevent someone from seeing who is invited, or if they "Reply All" to a calendar invite, all invitees will not be emailed. It is like BCC but for calendar invites.
Here is how to do it:
Step 1: Navigate to Outlook Web Calendar on your browser.
Step 2: Click on New Event 
Step 3: Click on Response Options, which is the icon to the right of your attendee list. 
Step 4: Make sure the Hide Attendee List option is enabled as illustrated in this picture:
When you have completed setting up your meeting invite, click Send.