We propose a scheme to generate a 4-qubit cluster of entangled coherent states in bimodal QED cavities. The scheme employs a single two-level atom that interacts dispersively with cavity modes initially prepared in coherent states. The fidelity and success probability of the state preparation are obtained considering the influence of atomic velocity spread and atomic efficiency detection. The scheme is also generalized for higher order cluster states. © 2008 IOP Publishing Ltd.