Biocomposites consisting of a conjugated linseed-oil (CLO)-based thermoset reinforced with rice hulls were prepared by free-radical polymerization initiated by t-butyl peroxide. The resin composition was kept constant at 50 wt % CLO, 35 wt % n-butyl methacrylate, and 15 wt % divinylbenzene. Tensile tests, dynamic mechanical analysis, thermogravimetric analysis, Soxhlet extraction, and differential scanning calorimetry were used to establish the ideal cure sequence. The pressure during cure, filler load, and the drying and grinding of the filler were varied, and their effects on the final properties of the composites were assessed. Optimal conditions were established for the preparation of rice hull biocomposites. Scanning electron microscopy showed a weak filler–resin interaction and X-ray mapping suggested the presence of silica in the rice hulls; this have accounted for the high thermal and mechanical properties obtained for these composites.