Although many studies have suggested positive effects for speaking or output practice on L2 grammar development, the question of how speaking affects L2 grammar remains. This study specifically examines how output affects the explicit and implicit knowledge of Spanish indirect object pronouns (IOPs). It also investigates levels of L2 grammar development for participants with low, mid and high levels of background knowledge of Spanish subject-verb agreement. Eight participants were given explicit grammar instruction on the target structure followed by six paired output-focus activities. These included two information-gap tasks, a matching task, a partner interview, original sentence creation, and a dictogloss task. In each task participants were required to orally produce IOPs whether they were reading a prepared IOP or producing one originally based on a prompt. In order to capture qualitative data on the effectiveness of output, all paired interaction was transcribed and coded for language related episodes (LREs). In this study three types of LREs were identified: self-correction, other-correction and metatalk. Learners were also tested on IOPs immediately before instruction, immediately following and three weeks afterward. Quantitative data consisted of these results of pre, post, and delayed posttests, the number of IOPs produced during all instructional activities, and the percentage of correct IOPs produced compared to those omitted or produced incorrectly. Development of explicit knowledge was assessed by an untimed written picture description task, whereas implicit knowledge was assessed on the tests by a timed grammaticality judgment task. The results of the picture description task showed more consistent gains in development of explicit knowledge. The results of the grammaticality judgment task were more irregular and suggested less consistent gains in development of implicit knowledge. Together, quantitative and qualitative results suggest that explicit instruction followed by output practice was most effective for learners in this study with greater knowledge of subject-verb agreement. A comparison of qualitative results and test scores revealed that learners who showed more focus on the lexicon during instructional tasks and did not produce IOPs as often, and also had lower scores on both tests. Stronger learning outcomes were observed for learners who produced more IOPs, had a higher percentage of correct IOPs and were involved in LREs.