The transonic buffet phenomenon over the OAT15A supercritical airfoil is investigated under high Reynolds number conditions (Rec = 3.0 × 106 , M∞ = 0.73) using wall-modeled large eddy simulation (WMLES). Following the methodology originally proposed by Kawai and Fukushima [1], WMLES is employed to alleviate the stringent near-wall resolution requirements of wall-resolved LES, enabling larger time steps and a significant reduction in computational cost while retaining the essential unsteady flow physics. The numerical framework is based on a continuous Galerkin spectral element method (CG-SEM) [2], which further reduces the degrees of freedom while preserving the high-order accuracy required for large eddy simulations. A central focus of the present study is the assessment of spanwise domain extent and resolution effects on the predicted transonic buffet dynamics. The results demonstrate that spanwise modeling has a pro- nounced influence on shock-wave/boundary-layer interactions, shock-induced separation, and the devel- opment of coherent turbulent structures. In contrast to the results reported by Kawai and Fukushima [1], the present simulations exhibit different buffet characteristics and spanwise flow organization. These dis- crepancies are consistent with observations previously discussed by Haas and Housman [3], highlighting the sensitivity of transonic buffet predictions to three-dimensional effects. The findings underline the importance of adequate spanwise representation in WMLES [4] of transonic buffet and demonstrate that the combination of WMLES and CG-SEM provides an efficient and robust framework for the simulation of unsteady transonic flows over realistic airfoil geometries.