A finite element model was developed to assess the mechanical behaviour of pultruded glass fibre reinforced polymer (GFRP) box sections with embedded steel rods; the performance of these virtual specimens was compared with that of extruded aluminium sections with comparable dimensions. All specimens were tested in transverse loading and in torsion. A parametric study was carried out in order to optimize the stiffness of the GFRP-steel hybrid specimens. It was found that the modes of deformation exhibited by the GFRP-steel hybrid specimens were highly tunable. The hybrid members had sufficient bending stiffness when compared with equivalent extruded aluminium members; however, the technology will likely require further development to ensure adequate shear stiffness.