This study investigates whether lexical knowledge in the first language (L1) of late Turkish-Dutch bilinguals becomes less accessible for the production of fluent speech and in controlled experimental tasks as a result of extended stay in the Netherlands. It is also considered to what degree extra-linguistic factors can account for this phenomenon. Data are collected from the first generation Turkish migrants (n = 52) and from a monolingual reference group in Turkey (n = 52) via a lexical naming task, a free speech task and a sociolinguistic background questionnaire. The results show that the bilingual group is indistinguishable from the monolinguals on the experimental task. However, in the free speech task, they not only are significantly more disfluent than the monolinguals but also make significantly less use of diverse, in particular low-frequency, vocabulary. Overall, the results signal that bilinguals were outperformed by the monolinguals in spontaneous language production but not on a controlled task. The study interprets this finding to indicate a decrease of automaticity in the access to linguistic knowledge which impedes the rapid integration of information from all linguistic levels. Further analyses with respect to the relations between the L1 change and nonlinguistic factors are discussed within the Activation Threshold Hypothesis (ATH).