Vocabulary and sentence-level grammar skills are the bedrock on which fluent L2 reading skills rest. The importance of vocabulary knowledge in particular is self-evident-texts consist of words-but the actual contribution that individual differences in vocabulary knowledge make to L2 reading outcomes seems to vary. Greater vocabulary knowledge, as reflected in the basic dimension of size, correlates strongly with better reading outcomes (Laufer, 1992;Qian, 1999Qian, , 2002, but there are also studies that show little, or no, link between the two (Yamashita, 2013). The inconsistency is due to differences in target population, task, setting and other study-specific factors. It may also reflect the difficulty of the text relative to the readers' proficiency level. This study examines the relationship between L2 reading outcomes and reader based vocabulary and grammar knowledge as it is moderated (Hayes, 2013) by the text based features of lexical difficulty and syntactic complexity. By examining the potential interaction between reader knowledge and text demands, the study provides a more refined picture of the factors affecting reading outcomes, with a specific focus on vocabulary size, alone and in combination with sentence-level grammatical knowledge. The latter is also a potential moderating factor on the link between vocabulary knowledge and reading outcomes. Findings for RQ1 showed vocabulary knowledge was a stronger predictor than grammatical knowledge. This replicates previous studies showing the importance of vocabulary knowledge in explaining variation in L2 reading Zhang, 2012;Yamashita, 1999) and is at odds with other studies (Shiotsu & Weir, 2007;Shiotsu, 2010).Findings for RQ2 showed that lexical difficulty, as indexed by lexical frequency, accounted for more variation in reader outcomes than syntactic complexity. This finding supports previous findings (Brown, 2013;Eslami, 2014; Twessi, 1998). For RQ3 there was a mean interaction effect between lexical frequency and reader vocabulary knowledge such that the relationship between vocabulary and L2 reading for high lexical frequency texts was stronger than for low lexical frequency texts, but the effect was not statistically significant.There was no effect for differences in text syntactic complexity. The results also showed that text lexical frequency significantly moderated the relationship between reader grammatical knowledge and L2 reading, such that the relationship between grammatical knowledge and L2 reading for high lexical frequency texts was significantly greater than for low lexical frequency texts. Given the absence of significant interaction between vocabulary knowledge and lexical frequency, the sample was split into high and low vocabulary size groups (30% each) to see if more distinct proficiency differences would yield significant differences for lexical frequency effects. The subgroup analysis did not yield different results, though it did show that the grammatical knowledge-lexical frequency interaction evident in the complete ...