Composite materials have proven their applicability for various structural components. Glass fiber reinforced plastic (GFRP) composite materials have potential applications in aerospace, automobile related industries due to their excellent properties. Drilling is important operation for composite structures during final assembly. This paper investigates the factors affecting delamination in glass fiber reinforced plastic (GFRP) composite during the drilling process. Drill speed and feed rate are selected two parameters affecting delamination during the drilling process. Response surface methodology (RSM) approach has been used for experimental design and analysis of variance (ANOVA). Delamination evaluated at entry, middle and exit position of the hole. An attempt has been made to optimize speed and feed for minimization of delamination at these three positions using grey relational analysis (GRA). The results of this work will help in selecting an optimum level of speed and feed to minimize delamination at entry, middle, and exit position of the hole improving quality of the drilled hole.