This study set out to examine the range of legibility demonstrated by Western Australian students required to handwrite tasks of increasing intrinsic cognitive load. A representative sample of students in Years 1, 2 and 3 (N=437) was recruited for a cross sectional study and teachers administered handwriting tasks. Year 1 students were administered easier tasks (copying from the board and dictation), and Year 3 students were administered more difficult tasks (dictation and composition), whilst students in Year 2 were administered all three tasks. A rubric was then constructed for six aspects of legibility from selected participant exemplars: letter formation, size, space in word, space between words, line placement, and slant, providing 18 items for analysis (3 tasks x 6 aspects). The rubric demonstrated acceptable inter- and intra-reliability. Scores were assigned following pairwise comparisons; a Rasch model (RM) analysis was applied to scores. Fit to the RM was confirmed to permit a more accurate assessment of legibility. The study substantiates many assumptions about handwriting in the extant literature, and more specifically reveals how cognitive load governs legibility when students are learning to handwrite. Implications for practice are discussed.