Bare forms (or [slashed O] forms), uninflected lexical L2 insertions in contexts where the matrix language expects morphological marking, have been recognized as an anomaly in different approaches to code-switching. Myers-Scotton (1997, 2002) has explained their existence in terms of structural incongruity between the matrix and embedded languages, while Poplack (Budzhak-Jones and Poplack, 1997) looks to distributional symmetries or asymmetries with other anomalous phenomena such as non-standard case marking. In corpus-based studies, bare forms often emerge as clinal in nature, with full matrix language marking appearing alongside bare forms. This suggests that discrete structural constraints are not the only factors, nor necessarily always the dominant ones in play. In this paper it is proposed that on-line processing constraints governed in particular by lexical frequency effects and inherent latencies associated with inflectional attachment may lead to bare forms. The argument is based on a multilingual corpus of native Arabic speakers from the city of Maiduguri in northeastern Nigeria. [Funding for this research was provided by the German Research Council (DFG) via the special research project 560 centered at Bayreuth University.]