This study examines the visual processing of Arabic-English code-switching using an eye-tracking experiment, focusing on determiner-noun switching. Arabic-English bilinguals (L1 Arabic, L2 English) read English-framed sentences that were either monolingual or contained a code-switched noun phrase with an English determiner and an Arabic noun (e.g., John bought the كتاب) or an Arabic determiner and an English noun (e.g., John bought ال book). The Matrix Language Frame (MLF) model (Myers-Scotton, 1993, 2002) predicts that the matrix language (ML) determines the selection of functional elements, requiring determiners to come from English. However, eye-tracking results revealed the opposite pattern: codes-witching was more disfavored if the determiner came from English than if it came from Arabic, contradicting the MLF model’s predictions. These findings suggest that grammatical constraints alone cannot fully explain code-switching patterns and that orthographic differences, script directionality, and switching costs play a role in bilingual sentence processing.