I had the same problem - looked everywhere and could not find where to revoke OAuth tokens for connected apps. I finally found it today though.
- Sign in to Outlook.com
- Click your user icon at top right
- Click "View Account". This takes you to an account overview page on account.microsoft.com
- Click "Security & Privacy" on the menu bar
- There is an "Apps & Services" section there. Click the "Manage permissions" link in this section.
- You'll see a list of connected apps, you can click Edit to view/remove their access to your account