The results of two self-paced reading experiments are reported, which investigated the online processing of subject-object ambiguities in Dutch relative clause constructions like Dat is de vrouw die de meisjes heeft/hebben gezien by German advanced second language (L2) learners of Dutch. Native speakers of both Dutch and German have been shown to have a preference for a subject versus an object reading of such temporarily ambiguous sentences, and so we provided an ideal opportunity for the transfer of first language (L1) processing preferences to take place. We also investigated whether the participants' working memory span would affect their processing of the experimental items. The results suggest that processing decisions may be affected by working memory when task demands are high, and in this case the high working memory span learners patterned like the native speakers of lower working memory. However, when reading for comprehension alone and when only structural information was available to guide parsing decisions, working memory span had no effect on the L2 learners' online processing, and this differed from the native speakers' online processing even though the L1 and the L2 are highly comparable.