We consider a generalization of the SPMD programming model to orthogonal processor groups. In this model different partitions of the processors into disjoint processor groups can be exploited simultaneously in a single parallel implementation. The parallel programming model is appropriate for grid based applications working in horizontal or vertical directions as well as and for mixed task and data parallel computations[2]. For those applications we propose a systematic development process for message-passing programs using orthogonal processor groups. The development process starts with a specification of tasks indicating horizontal and vertical sections. A mapping to orthogonal processor groups realizes a group SPMD execution model and a final transformation step generates the corresponding message-passing program.