The effects of rotation and magnetic field on the onset of oscillatory modes of Benard-Marangoni instability in a horizontal fluid layer with a deformably free surface are investigated numerically. The derived eigenvalue equations are solved using the fourth order Runge-Kutta-Gill＇s method coupled with the Broyden＇s method. The results show that the Crispation number C, associated with the deformation of the upper surface, is significant on the Benard-Marangoni instability. The system is Stabilizing, as the Blot number Bi, the Bond number Bo, the Taylor number T and the Chandrasekhar number Q increase. The absolute value of critical Marangoni number \M-c\ in the (\M-c\,- R)-plane decreases linearly with increasing Rayleigh number R.