This dissertation investigated what memory mechanisms support parsing and how they constrain sentence comprehension during first-language (L1) and second-language (L2) sentence reading. Although two memory-based accounts in sentence processing research, the capacity-based model (Just & Carpenter, 1992; King & Just, 1991) and the cue-based retrieval model (McElree & Vasishth, 2005; McElree, Vasishth, & Van Dyke, 2006; Nicenboim & Vasishth, 2018), demonstrated memory mechanisms supporting sentence comprehension, how readers access linguistic representations outside focal attention during reading is a largely unresolved issue, especially in L2 processing. Thus, the current research compared the predictions of the cue-based retrieval model and the capacity-based model in sentence comprehension using eye-tracking. Based on previous evidence for the cue-based retrieval model, this dissertation also examined whether enhancing the quality of lexical representations through semantic elaboration influences retrieval efficiency, given the assumption that providing additional semantic information for the target and/or the distractor increases the uniqueness of the target representation in memory by reducing similarity-based retrieval interference. Importantly, in order to understand whether the ability to use an efficient, cue-driven operation determines skilled versus less-skilled reading, L1 and L2 speakers’ reading patterns were compared. The findings that both L1 and L2 readers were sensitive to similarity-based retrieval interference during sentence comprehension suggest that sentence processing relies on a series of cue-based retrievals, but the ability to employ this operation itself may not distinguish skilled reading from less-skilled reading. In particular, the observed L1-L2 differences in reading patterns suggest that the most likely predictor of reading ability may be individuals’ quality of lexical representation