The ability to coordinate serial processing of multiple items is crucial for fluent reading but is known to be impaired in dyslexia. To investigate this impairment, we manipulated the orthographic and phonological similarity of adjacent letters online as dyslexic and nondyslexic readers named letters in a serial naming (RAN) task. Eye movements and voice onsets were recorded. Letter arrays contained target item pairs in which the second letter was orthographically or phonologically similar to the first letter when viewed either parafoveally (Experiment 1a) or foveally (Experiment 1b). Relative to normal readers, dyslexic readers were more affected by orthographic confusability in Experiment 1a and phonological confusability in Experiment 1b. Normal readers were slower to process orthographically similar letters in Experiment 1b. Findings indicate that the phonological and orthographic processing problems of dyslexic readers manifest differently during parafoveal and foveal processing, with each contributing to slower RAN performance and impaired reading fluency. (Contains 5 tables, 5 figures and 1 footnote.)