Abstract: This pilot study examined the development of complexity and fluency of second language (L2) spoken production among L2 learners who received extensive practice on grammatical chunks as constituent units of discourse. Twenty-two students enrolled in an elementary Japanese course at a U.S. university received classroom instruction on 40 grammatical chunks through communicative drills and memorization of dialogues that contained the target chunks. The students completed two spontaneous conversation tasks in Japanese at five-week intervals during the semester. Development of their speech between the first and second conversation task was analyzed from three perspectives: 1) the number of accurately used chunks, 2) the complexity of utterances (the number of chunks per t-unit), and 3) oral fluency (pause length and speech rate). Matched-pair t tests revealed significant gains in the number and range of the grammatical chunks produced over time, as well as in the complexity of individual utterances. However, there were no significant gains in the fluency of oral production.