We have search bar for almost all features. I just compared it with other pages, and found that it is missing for usergroups.

The version I'm using is:
foreman-installer-1.4.0-0.develop.201312171100git39bac59.el6.noarch
foreman-1.4.0-0.develop.201312191501gitf8e7098.el6.noarch
foreman-release-1.4.0-0.develop.201312191501gitf8e7098.el6.noarch

Request you to take a look and fix it, since it would be easier to find a usergroup via search then later update it.