The current study investigated the effects of three forms of output activity on EFL learners' recognition and recall of second language (L2) vocabulary. To this end, three groups of learners of English as a foreign language (EFL) were instructed to employ the following three output activities after reading two narrative texts: (1) summarizing the texts and incorporating target vocabulary in the summary; (2) generating several general comprehension questions out of reading texts and answering those questions while incorporating target vocabulary; and (3) making predictions about what is to occur in the texts and including target vocabulary in the prediction. The results of a cued response production test and a multiple choice recognition test indicated that the three treatment conditions resulted in significant development of vocabulary knowledge. Moreover, the results revealed that making predictions and questioning/answering were more effective than summarizing for promoting L2 words knowledge.