Global Combine fields filter (Views) does not include Referenced Entities (Content Type)
This is not possible with Global Combine fields filter at the moment, see also the feature request for the Entity reference module.

This is possible though with the Views filters populate module. You can use any field of a referenced entity or field collection of which you setup the relation with in your view.

Howto :


Like the instructions on the module's page describe, first step is to
add the fields you want to search on in an OR combination of filters.
With Drupal6 that would have been by using the 'Views Or' module; with
Drupal7 this is just a filter group with internal operator set to
'Or'. These individual filters should  not be exposed.
Then these filters can be exposed as one input by adding the module's provided filter called 'Populate filters', found on the 'Global' section. Expose it and check the filters you added in the Or group.