Slender webs of glass fiber-reinforced polymer (GFRP) beams are sensitive to shear buckling. Shear buckling can bee seen as an in-plane biaxial compression-tension buckling problem. The transverse tensile load thereby delays the onset of buckling and increases the ultimate load. Thin-walled GFRP plates of two different fiber stacking sequences, [0/90]S and [90/0]S, were subjected to in-plane biaxial compression-tension loading. The buckling loads were almost duplicated by increasing the tensile load while the ultimate loads were increased by up to 20%. The fiber stacking sequence thereby had significant effects on buckling mode shape and buckling and ultimate loads.