Oilseed rape straw was steam exploded into hot water at a range of severities. The residues were fractionated into solid and liquid phases and chemically characterised. The effect of steam explosion on enzymatic hydrolysis of the water-insoluble fractions was investigated by studying initial cellulase binding and hydrolysis yields for different cellulase doses. Time-course data was modelled to establish rate-dependent differences in saccharification as a function of pretreatment severity and associated chemical composition. The study concluded: (1) the initial hydrolysis rate was limited by the amount of (pectic) uronic acid remaining in the substrate; (2) the proportion of rapidly hydrolysable carbohydrate was most closely and positively related to lignin abundance and (3) the final sugar yield most closely related to xylan removal from the substrate. Comparisons between milled and un-milled steam exploded straw highlighted the influence that physical structure has on hydrolysis rates and yields, particularly at low severities. (C) 2014 Published by Elsevier Ltd.