In this study, reducing the density of oriented strand board (OSB) in the core layer where strands were replaced by rape straw particles was evaluated. The use of rape particles in the core layer did not significantly affect the mechanical properties of OSB. This type of board had only slightly deteriorated properties compared with conventional OSB. However, with a decreasing density, significant changes occurred in the modulus of rupture (MOR) and modulus of elasticity (MOE) determined for the shorter axis. The lowest possible density value was determined based on statistical analysis, allowing for the production of OSB that met the requirements of EN 300 (2006) for OSB type 3. The analysis showed that panels of this type can be produced at a density of 530 kg/m3.