We summarize findings from across a range of methods, including behavioral measures of overall processing speed and accuracy, electrophysiological indices that tap into the early time course of language processing, and neural measures using structural and functional imaging. We argue that traditional claims about rigid constraints on the ability of late bilinguals to exploit the meaning and form of the morphology and morphosyntax in a second language should be revised so as to move away from all or none command of structures motivated from strict dichotomies among linguistic categories of morphology. We describe how the dynamics of morphological processing in neither monolingual or bilingual speakers is easily characterized in terms of the potential to decompose words into their constituent morphemes and that morphosyntactic processing is not easily characterized in terms of categories of structures that are learnable and those that are unlearnable by bilingual and nonnative speakers. Instead, we emphasize the high degree of variability across individuals and plasticity within individuals in their ability to successfully learn and use even subtle aspects of a second language. Further, both of the bilingual’s two languages become active when even one language is engaged, and parallel activation has consequences that shape both languages, thus their influence is not in the unidirectional manner that was traditionally assumed. We briefly discuss the nature of possible constraints and directions for future research.