This study investigated the roles of phoneme position, stress, and proficiency in L2 spelling development by Taiwanese students learning English as a Foreign Language (EFL), an alphabetic writing system typologically different from the learners' L1 logographic system. Structured nonword spelling tests were administered to EFL sixth-graders with lower and higher English proficiency level. The results showed that overall, final phonemes were spelled more poorly than their initial and medial counterparts; however, phoneme position effect decreased as learners' English proficiency improved. Secondly, spelling of the stressed syllable was significantly better than that of the unstressed syllable. However, when phonemes were held constant, stress effect was significant only in the first, but not in the second syllable. Thirdly, higher proficient EFL children spelled significantly better than their lower proficient counterparts, and spelling errors were more systematic in the former. The findings of the study are discussed from linguistic, psychological, and developmental perspectives.