Listing yum group
Try yum groupinfo
From the groupinfo section of the manpage:
Is used to give the description and package list of a group (and which type those packages are marked as). Note that you can use the yum-filter-data and yum-list-data plugins to get/use the data the other way around (Ie. what groups own packages need updating). If you pass the -v option, to enable verbose mode, then the package names are matched against installed/available packages similar to the list command.