摘要:This study sought to investigate the patterns of and possible reasons for Language-Switching (L-S) behavior of Iranian EFL learners engaged in L2 composing task. The findings revealed that the subjects needed to switch to their L1 in order to: 1) generate ideas, 2) search for L2 equivalent, 3) revise and correct errors, 4) plan the task, 5) establish the coherence of ideas, and 6) confirm lexical meaning. The results also demonstrated the participants switched to their L1 for the following reasons: 1) Linguistic deficiency, 2) Overload of memory and 3) Ease with native language. The results indicate that encoding certain non-linguistic feelings or experiential mental images is cognitively demanding and would need to be accessed via L1_ the stronger language of a bilingual person.