Here is how you can create a GA4 ‘Content Group‘ Report in BigQuery.

A content group is a collection of web pages that share a common theme.
For example, in a blog, a content group could consist of web pages covering the same topic, such as Google Tag Manager.
For an e-commerce website, a content group might include pages that sell similar products, such as shirts.
Content groups help measure the performance of a set of web pages at a content category or product category level.
They are particularly useful for large websites with hundreds or thousands of pages, where analyzing individual page-level performance is impractical.
Follow the steps below to create a content group report in GA4 BigQuery:
Step-1: Make sure you have set up content groups in your GA4 property via GTM and collected at least a couple of days of content group data in both your GA4 property and BigQuery data tables.
Step-2: Once you have successfully set up ‘content_group’ for a website, you should see the value of the ‘content_group’ event parameter with the ‘page_view’ event in your GA4 BigQuery data table.

If you have successfully set up ‘content_group’ for a mobile app, then you should see the value of the ‘content_group’ event parameter with the ‘screen_view’ event in your GA4 BigQuery data table.