The current study investigates the effect of auditory and visual speech information and orthographic information on second/foreign language (L2) acquisition. To test this, native speakers of Turkish (a language with a transparent orthography) and native speakers of Australian English (a language with an opaque orthography) were exposed to Spanish (transparent orthography) and Irish (opaque orthography) legal non-word items in four experimental conditions: auditory-only, auditory-visual, auditory-orthographic, and auditory-visual-orthographic. On each trial, Turkish and Australian English speakers were asked to produce each Spanish and Irish legal non-words. In terms of phoneme errors it was found that Turkish participants generally made less errors in Spanish than their Australian counterparts, and visual speech information generally facilitated performance. Orthographic information had an overriding effect such that there was no visual advantage once it was provided. In the orthographic conditions, Turkish speakers performed better than their Australian English counterparts with Spanish items and worse with Irish terms. In terms of native speakers' ratings of participants' productions, it was found that orthographic input improved accent. Overall the results confirm findings that visual information enhances speech production in L2 and additionally show the facilitative effects of orthographic input in L2 acquisition as a function of orthographic depth. Inter-rater reliability measures revealed that the native speaker rating procedure may be prone to individual and socio-cultural influences that may stem from internal criteria for native accents. This suggests that native speaker ratings should be treated with caution. / Master of Arts (Hons)