This study contributes to L2 writing research which seeks to tie predictions of the Limited Attentional Capacity Model (Skehan, 1998; Skehan & Foster, 2001) and Cognition Hypothesis (Robinson, 2001, 2005, 2011a, 2011b) to models of working memory in L1 writing (Kellogg, 1996). The study uses a quasi-experimental research design to investigate distinct forms of pre-task planning (idea generation, organization, and goal setting) and their effect on essays composed by a large homogeneous group of Spanish-speaking EFL learners. Quantitative measures of writing fluency, grammatical complexity, and lexical complexity are statistically compared among five pre-task planning conditions. Pre-task planning condition was found to have a small significant effect on writing fluency, whereas pre-task planning condition was found to have no impact on lexical complexity and grammatical complexity. The authors discuss their findings by suggesting that the predictions of the Limited Attentional Capacity Model and Cognition Hypothesis may not be applicable to writing, that the effects of pre-task planning in earlier L1 and L2 research may have been moderated by the participants' education and genre knowledge, and that a threshold level of general L2 proficiency may be necessary for pre-task planning to impact L2 writers' texts. (Contains 3 tables.)