Testing in second language (L2) research is of utmost importance as the type of measure employed can substantially influence the observed outcomes and the theoretical as well as pedagogical claims derived from them. Currently, L2 research is heavily biased toward using offline measures, most of which do not tap into learners’ authentic L2 competence. This article, therefore, proposes alternative assessment measures in L2 research. These measures, referred to as online measures or tests, are informed by psycholinguistic approaches to real-time language processing. The article begins by providing a justification for the need to use online tests in L2 research and moves on by discussing the nature of language and language acquisition in order to establish the rationale behind adopting these tests. It then elaborates on these measures by providing detailed explanations and illustrative examples. To further elaborate on how online measures may be employed in L2 research, the article also reviews a number of studies adopting these measures in their design. Finally, the article discusses the methodological and interpretative considerations associated with the use of online measures and concludes by highlighting the importance of incorporating these measures into L2 research.