Multicast is an important collective communication in scalable parallel computers. One efficient scheme to perform multicast is multidestination messaging. In multidestination messaging, destination nodes of a multicast are partitioned into disjoint groups. Nodes in each group are reached with a multidestination message that conforms to the base routing algorithm of the system. A systematic way of partitioning the nodes is thus critical to multidestination messaging. In this paper we propose a node grouping method, called turn grouping, for partitioning the destination nodes in a multicast. Turn grouping supports any base routing algorithm derivable from the turn model. Simulations based on three turn model-based routing algorithms show that our approach performs better than the some the others.