It is now generally agreed that "output" functions to promote language learning through focus on form. Empirical studies reveal that oral communicative tasks can arouse learners' negotiation of meaning, but they are not so effective in bringing about focus on form. Hence, researchers have suggested using collaborative writing tasks to enhance language learning, for which positive empirical evidence has been obtained. However, no studies have examined how collaborative writing tasks and oral communicative tasks are different in impacting upon learners' attention to language forms. This paper reports on a study which investigates English as a foreign language (EFL) learners' focus on form in performing a collaborative oral task and a collaborative writing task. Eight pairs of participants completed the two tasks, with their performances being videotaped. Based on the transcripts of their talk, participants' attention to language forms was analysed through identifying and coding their language-related episodes (LREs) qualitatively followed by the quantification of these episodes. The results reveal that the written output pairs and the oral output pairs attended to language forms differently in both quantity and quality. The findings are discussed with reference to the differences of written output and oral output in cognitive demand, task nature, and language learning potential engendered. (Contains 4 tables and 1 figure.)