Hi Ctvu,
Please try the following steps to reset Microsoft Sync Services to check whether the issue still exists.
1. Quit all applications.
2. On the Go menu, click Home.
3. Open Library.
Note The Library folder is hidden in Mac OS X Lion. To display this folder, hold down the OPTION key while you click the Go menu.
4. Open Preferences. Drag the following files to the Trash:
o com.microsoft.Outlook.SyncServicesPreferences.plist
o com.microsoft.Outlook.SyncServices.plist (if it exists)
o OfficeSync Prefs (if it exists)
5. While you are still in Preferences, open Microsoft, and then open Office 2011.
Note: If you have Service Pack 2 installed, open Application Support > Microsoft > Office 2011 instead of Preferences> Microsoft > Office 2011.
6. Drag OfficeSync Prefs to the Trash, and then close the window.
7. On the Apple menu, click Restart.
8. Open Outlook 2011.
9. On the Outlook menu, click Preferences.
10. Under Other, click Sync Services.
11. Select the check boxes for the items that you want to sync.
12. Close the window.
Moreover, please try creating a contact in OWA, Quit Outlook 2011 and reopen it to check whether the contact is in Mac Contact.
Thanks,
Yang Yu