Drupal CiviCRM Entity in Rules: How to loop over all members of a group?
You can use the Views Rules module: https://www.drupal.org/project/views_rules

This will provide a Views Loop: from the project page: "A view loop is similar to a regular Rules loop, but allows looping over rows of view results."

So enable that module, and then create a view that lists contacts that are in the group you desire.  

Some basic instructions from the Views Rules project page:

Install the module (and make sure Rules UI and Views UI are both enabled)
Configured Views
    Add a view (with some fields)
    Add a "Rules" display
    Configure row variables
    Save
Configure Rules
    Add a rule
    Add the "Collect view result rows" action or add a view loop
    Select the "Rules" display
    Configure the parameters and variable names
    [Do what you want with the newly available variables]