In this paper, we propose a modified overlapped block matching (OBM) scheme for stereo image coding. The OBM scheme has been introduced in video coding, as a promising way to reduce blocking artifacts by using multiple vectors for a block, while maintaining the advantages of the fixed size block matching framework. However, OBM has its own limitations, even though it overcomes some drawbacks of block matching schemes. For example, to estimate an optimal displacement vector (DV) field, OBM requires complicated iterations. In addition, OBM does not always guarantee a consistent DV field, even through several iterations, because the estimation considers only the magnitude of the prediction error as a measure. Therefore, we propose a modified OBM scheme, which allows both consistent disparity estimation and efficient disparity compensation, without several iterations. In the proposed scheme, the computational burden resulting from iterations is reduced using 'open-loop' coding, which decouples the encoding into estimation and compensation. The consistent disparity estimation is performed by using a causal MRF model and a half-pixel search, while maintaining (or reducing) the energy level of disparity compensated difference frame. The compensation efficiency is improved by interpolating the reference image in half pixel accuracy and by applying OBM in part. To prove the efficiency of the proposed OBM scheme, we provide some experimental results, which show that the proposed scheme achieves higher PSNR, about 0.5 - 1 dB, as well as better perceptual quality, at a fraction of the computation, as compared to a conventional OBM.