Numerous studies in the SLA literature document the advantages of Processing Instruction over traditional instruction methods (e.g., VanPatten & Oikkenon, 1996; Benati, 2001; Wong, 2004; Fernández, 2008). A common finding of many of those studies is that as long as learners are exposed to structured input, explicit information offers no additional benefit in the learning process. Structured input is defined as practice that requires learners to attend to the grammatical item (Lee & VanPatten 1995), pushing them to process the targeted form (VanPatten 2000) so that a connection between form and meaning is made (VanPatten 2004). Effectively, what such conditions spell out is that structured input practice should be task-essential, i.e., that "the task cannot be successfully performed unless the structure is used" (Loschky & Bley-Vroman 1993). Indeed, virtually all research studies implementing structured input use task-essential activities in both treatment and exit tests. In light of these facts, questions arise as to a) the extent to which the benefits attributed to Processing Instruction originate in task-essentialness and b) whether explicit information might only be superfluous if practice fulfills that condition. The present study sought to address these issues through an empirical study with a pre-, post- and delayed posttest design. The variables +/- explicit information and +/- task-essential were combined to form four experimental conditions. A control group was added to obtain a baseline. One hundred and thirty learners of Spanish randomly assigned to each group completed a treatment on the ser/estar copula distinction and object-verb-subject structures. Findings suggest a) that structured input needs to be task-essential in order for its benefits to obtain, b) that in the absence of task-essential practice explicit information becomes necessary and c) that benefits obtained from explicit information are both more consistent and more durable than those obtained from task-essential practice.