Automated fiber placement (AFP) machines can steer the fibers/tows to make the so-called variable stiffness (VS) composites. They allow the designers to fully exploit the directional properties of composite materials to tailor the internal load distribution and improve the structural performance. VS composites have been shown to be very promising in the design optimization of composite panels and shells for buckling and post-buckling performance and consequently for further reducing the mass of future aerospace structures. In this chapter, the buckling performance improvement of VS composite cylinders with circular and elliptical cross sections is investigated. A metamodeling based design optimization (MBDO) method is presented to maximize the buckling performance of VS composite cylinders compared with their constant stiffness (CS) designs. The structural improvement mechanism via stiffness tailoring in a VS composite cylinder is also presented and discussed. The effects of different parameters including the cylinders’ aspect ratio and size as well as the percentage of the steered plies in the laminate are also investigated.