The paper presents the application of an optimization procedure to the aero-thermal design of high performance turbomachinery cascades. The blade profiles are parameterized with third-order Bezier polynomials for the pressure and suction sides, and quadratic functions for the leading and trailing edges, according to the composite curve approach. Evidence is given that fairly complicated blade shapes are well approximated by the present parameterization. The method is applied to an existing nozzle guide vane for which extensive and detailed experimental data are available, with the objective of decreasing in an integral sense the thermal load, maintaining or increasing the blade efficiency and the aerodynamic load. The results demonstrate that, despite the excellence of the initial design, there is room for improvements.