In the present investigation, influences of process parameters such as pulse current, pulse on time, gap voltage, and sample compositions on the machining of hybrid Al-Al2O3/ B4C composites through wire electrical discharge machining (WEDM) are carried out. The parameters were optimized to minimize both material removal rate (MRR) and surface roughness (SR) through Taguchi and Grey relational analysis. The hybrid Al-Al2O3/ B4C MMCs containing the micro-particles of Al2O3 (purity 99 % and 100-325 mesh size) and B4C (purity 99% and 400 mesh size) were prepared by stir casting with varying proportions (i.e. 100/0, 75/25, 50/50, 25/75 and 0/100) of Al2O3 and B4C as a reinforcements. The morphology of the machined samples was also examined through SEM and found the presence of micro-ridges, micro craters, micro-cracks, black patches, debris, and micro-voids. The experimental results revealed the optimal grouping of process parameters as sample composition of B75A25 (75% B4C +25% Al2O3), pulse on time of 32 μs, pulse current of 2 A, and gap voltage of 40 V.