Processing instruction (PI) is a language teaching technique based upon the model of input processing developed by VanPatten (1993, 1996, 2002, 2004). The present study investigated the effects of PI as well as two other experimental conditions (traditional instruction and control) on the acquisition of the Spanish copulae ser and estar by 66 Chinese university students enrolled in a blended (partially presential and partially online) fourth-semester language course. The PI treatment condition included non-paradigmatic grammar explanations, processing strategies designed to help learners avoid commiting errors they may be predisposed to make, and structured input activities which eliminate redundant features of language that may make difficult the establishment of form-meaning connections. The traditional instruction (TI) treatment condition included paradigmatic explanations of grammar as well as production-based activities and exercises. Participants assigned to the control condition did not receive any instruction during the course of the study. The results of an experiment comparing the effects of each treatment condition on learners' scores on the Knowledge Test of Spanish Copulae, a measurement instrument designed for this study, found PI to be superior to TI at the immediate posttest level for tasks of interpretation and production. However, mean difference scores for the PI group were not significant when compared to those of the control group. Moreover, the learning gains exhibited by the PI group at immediate posttest were not durative, as they were not significant at the delayed posttest.