The primary objectives of this study are to investigate effects of varying design parameters on the tube action and shear lag behavior of a typical reinforced concrete bundled tube building, and propose optimal design approaches for similar structures. A parametric study was conducted with selected key design variables on the performance of a 41 story building. The design variables considered for the parametric study include the column depth, beam depth, column width and beam width of the moment frames. The performance of each model was assessed in terms of overall and critical (maximum) story drifts, and shear lag behavior. Overall, the effects of the column depth on the tube action and shear lag behavior were more prominent than the other member dimensions.