The impact of task complexity on integrated writing performance is under-researched. This study purports to investigate the effect of graph complexity and planning time on graph writing performance as well as graph description strategies. Ninety-six EFL learners of English were assigned into three groups to examine the effect of three planning conditions, that is, pretask planning, within-task planning, and no planning. Moreover, graph complexity, operationalized as the number of visual chunks in a graph, was the within-subject variable. In general, there were some benefits of graph complexity for syntactic complexity and some planning benefits for fluency, accuracy, and lexical diversity. However, graph complexity had a negative impact on accuracy, and measures of lexical sophistication were not affected in any condition. On the graph description side, pretask planning and graph complexity had a positive impact on graph description strategies. The theoretical and pedagogical implications of these findings are discussed.