A within-subject pretest-posttest comparison design was used to explore the effectiveness of a planning and writing intervention in improving the argumentative writing performance of five fourth-grade students with learning disabilities. Students were taught to collaboratively plan and revise their essays and independently write their essays using procedures articulated by Wong, Butler, Ficzere, and Kuperis (1996). Results demonstrated notable increases in students' written protocols on the quantitative criteria (e.g., number of words written, prewriting and composing times). However, only three of the five students made gains related to writing clarity and cogency. Students' performance improved from "below basic" to "basic" or "proficient" levels with respect to qualitative criteria (i.e., focus, content, and organization) on the statewide writing assessment. Although transfer effects to a different writing task, person, and setting were evident for all students on the quantitative criteria, these effects were mixed on the qualitative criteria. Social validity data indicated student and teacher satisfaction with the planning/writing intervention. Implications of the study for argumentative essay writing instruction are discussed.