Frequency Tunable Microwave absorbers in desired low thickness is a critical requirement in electronics, radar and military applications where Electro Magnetic Interference has become a major concern. Composite are obvious choice of absorbers in above applications. The aim of this paper is to investigate the use of carbon fiber grid layers as Frequency Selective Surface (FSS) on Carbon Filler based Glass-Epoxy composites. In this work, three key points are highlighted, first is design, modeling of FSS grid, using equivalent circuit model and Transmission Line Theory, second is the use of fillers including Milled Carbon Fibers and Carbon Nano Tubes (CNTs) for microwave absorption, third is to have the desired reflection loss at specified thickness of around 6-7 mm which is low as compared to recent trends. It is found that the factors like the number of grid layers , their unit cell dimensions, type of filler, and the top surface layer, affects the resonance frequency and hence the microwave absorption characteristics of the composite laminates. The results are satisfactory showing minimum of -9.8 Db of Reflection Loss at 6-7 mm thickness laminates, for varied range of frequency.