In this study, the effect and optimization of cutting parameters on surface roughness in a CNC turning operation was investigated by using the Taguchi method. The experimental studies were conducted under varying cutting speeds, feed rate, depth of cut and approach angle. An orthogonal array, the signal-to noise (S/N) ratio, and analysis of variance (ANOVA) were employed to study the performance characteristics in turning of hypereutectic Al-Si-Mg alloys produced by conventional and stir casting techniques.  The alloys under investigation were prepared by controlling melt using induction heating and melting furnace. The cutting operations were carried out under dry conditions on a CNC turning centre using coated carbide inserts. The conclusions revealed that the feed rate and cutting speed were the most influential factors on the surface roughness The optimal conditions obtained for surface roughness for the Al-20Si-0.05 Mg-1.2Fe developed by stir cast technique is more significant then those developed by conventional technique.