The　authors　consider　a　cooperative　output　regulation　problem　(for　short,　CORP)　for　linear　multi-agent　uncertain　multivariable　systems　by　distributed　output-feedback　control.　Specifically,　based　a　specific　coordinate　transformation　to　establish　a　multi-input　multi-output　(MIMO)　output-feedback　norm　form,　we　are　able　to　develop　a　novel　class　of　internal　model-based　protocols　for　the　problem.　Compared　with　existing　designs　in　the　recent　literature,　the　proposed　result　is　strictly　extended　and　applicable　to　multivariable　dynamical　networks　with　unknown　parameters　or　undergoing　large　parametric　uncertainties.　The　result　is　also　illustrated　by　a　benchmark　mass-spring　system.　©　2017　IEEE.