Switchgrass (SWG) has been used as a filler to produce conjugated linseed oil-based green composites. The effect of the amount of the SWG; the matrix crosslink density; and the incorporation of a compatibilizer, maleic anhydride (MA), on the structure, water absorption, and thermal and mechanical properties of the composites has been investigated. The thermal stability of the composites is primarily dependent on the amount of the SWG fibers, which are far less thermally stable than the linseed oil-based resin. For the most part, improvements in the mechanical properties can be achieved by increasing the amount of SWG (up to 70 wt %), increasing the amount of the crosslinker, and adding MA to increase the fillermatrix interaction. The uptake of water in the composites is mostly influenced by the loading of the SWG fibers. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 127: 1921-1928, 2013