Self-paced reading tests (SPRs) are being increasingly adopted by second language (L2) researchers. Using SPR with L2 populations presents specific challenges, and its use is still evolving in L2 research (as well as in first language research, in many respects). Although the topic of several narrative overviews (Keating & Jegerski, 2015; Roberts, 2016), we do not have a comprehensive picture of its usage in L2 research. Building on the growing body of systematic reviews of research practices in applied linguistics (e.g., Liu & Brown, 2015; Plonsky, 2013), we report a methodological synthesis of the rationales, study contexts, and methodological decision making in L2 SPR research. Our comprehensive search yielded 74 SPRs used in L2 research. Each instrument was coded along 121 parameters, including: reported rationales and study characteristics, indicating the scope and nature of L2 SPR research agendas; design and analysis features and reporting practices, determining instrument validity and reliability; and materials transparency, affecting reproducibility and systematicity of agendas. Our findings indicate an urgent need to standardize the use and reporting of this technique, requiring empirical investigation to inform methodological decision making. We also identify several areas (e.g., study design, sample demographics, instrument construction, data analysis, and transparency) where SPR research could be improved to enrich our understanding of L2 processing, reading, and learning.