The frictional effect of collisions of ionized with neutral atoms on the Taylor instability of a composite plasma in porous medium is considered in presence of a variable horizontal magnetic field. The system is stable for stable density stratification. The magnetic field can stabilize a system which was unstable in its absence. The medium permeability has a decreasing or an increasing effect on the growth rates. With the increase in collisional frequency, the growth rates decrease but may have increasing influence in certain region.