Our understanding of spelling development has largely been gleaned from analysis of children's accuracy at spelling words under varying conditions and the nature of their errors. Here, we consider whether handwriting durations can inform us about the time course with which children use morphological information to produce accurate spellings of root morphemes. Six-to 7-year-old (n = 23) and 8-to 11-year-old (n = 25) children produced 28 target spellings in a spelling-to-dictation task. Target words were matched quadruplets of base, control, inflected, and derived words beginning with the same letters (e.g., rock, rocket, rocking, rocky). Both groups of children showed evidence of morphological processing as they prepared their spelling; writing onset latencies were shorter for two-morpheme words than control words. The findings are consistent with statistical learning theories of spelling development and theories of lexical quality that include a role of morphology. Spelling has long been considered a window into how children think about words (e.g., Morris & Perney, 1984; Ouellette & Sénéchal, 2008; Treiman, 1998). We have learned a great deal through naturalistic and experimental research examining both children's spelling accuracy and their errors. For instance, children are more likely to include the penultimate /n/ in spelling two-morpheme words such as pinned than in one-morpheme words such as wind, suggesting a reliance on morphemes, the smallest units of meaning in language, in spelling (e.g., Treiman & Cassar, 1996; Treiman, Cassar, & Zukowski, 1994). We extend this evidence to explore the mechanisms underlying morphological processing during spelling. We build on recent adult research (Quémart & Lambert, 2017) to establish the utility of children's handwriting durations as offering insight into the time course of the processes children use before and during spelling of two-morpheme words. Changes with age in children's processing during spelling: studies of spelling production Behavioural studies show that children use morphemes in their spelling from an early age. Most evidence comes from the product of spelling processes, particularly spelling accuracy. For instance, Deacon and colleagues showed that children as young as 6 are more likely to spell whole root words correctly in inflected and derived words than in one-morpheme comparison words. Children are more likely to spell rock correctly in its two-morpheme relatives rocking and rocky than in the singlemorpheme word rocket (Deacon, 2008; Deacon & Bryant, 2006a, 2006b). Similar evidence comes from effects of morphology on children's spellings of single letters. For instance, 5-year-olds are more likely to spell the alveolar flap correctly as t when it is part of a root (e.g., dirty) than when it is not (e.g., city; Treiman et al., 1994; see also Treiman & Cassar, 1996).