This study evaluated physical, mechanical and fire properties of oriented strand boards (OSB) covered with fire retardant treated veneers. The beech (Fagus orientalis Lipsky) veneers were treated with either monoammonium phosphate, diammonium phosphate, lime water or a borax/boric acid (1:1 by weight) mixture. Physical and mechanical properties of the specimens were performed according to EN and DIN standards. A cone calorimeter was used to determine their combustion characteristics. The physical and mechanical properties of the specimens were adversely affected by the treatments. The specimens treated with lime water had the best physical performance while the specimens treated with borax/boric acid had the highest mechanical properties. The fire retardant treatments of the face veneers were effective in reducing the initial contribution of heat release to potential fire growth. In particular, the lime water treatment was an effective fire retardant treatment in that it reduced both the effective heat of combustion and the mass loss rate. It also delayed the times for sustained ignition.