The present study investigates the effects of controlled writing tasks on L2 college students' grammatical knowledge gains. Eighty-two participants with a low-intermediate English proficiency level were randomly assigned to an ordering task group, a grammatical transformation group, and a control group. In the study, a background questionnaire, pre- and post-grammar learning strategy questionnaires, and pre-, post-, and delayed grammar recognition tests were utilized. The findings of the study reveal that ordering tasks showed a significant effect on learners' short-term grammar gains while the two controlled writing conditions, ordering and grammatical transformation tasks, were more influential than the control group was on long-term memory. In addition, learners involved in ordering tasks indicated a positive attitude towards affective grammar learning strategies. This research raises several pedagogical implications and also offers suggestions on how language educators could implement the findings of this study into their L2 grammar instruction.