The study reported in this article aimed to investigate the way working memory capacity (WMC) interacts with careful online planning--a task-based implementation variable--to affect second language (L2) speech production. This issue is important to teachers, because it delves into one of the possible task-based implementation variables and thus could assist them in making empirically informed decisions in the classroom. It also bears significance for second language acquisition (SLA) researchers, in that it could help them test claims regarding the nature of interlanguages as well as the validity of speech production models that are essential in discussing the role and psycholinguistic functioning of planning in L2 performance and L2 acquisition. (Contains 2 tables.)