Look at multisearch http://rubyforge.org/pipermail/ferret-talk/2007-May/003275.html http://projects.jkraemer.net/acts_as_ferret/rdoc/classes/ActsAsFerret/ClassMethods.html#M000014
or combine searches over individual models http://infovore.org/archives/2006/09/22/cross-model-searching-in-rails-with-ferret/