Abstract This paper presents case-studies of language mixing within verbs and nouns in the heritage language American Norwegian, which refers to varieties spoken by Norwegian immigrants to the US and their descendants. The paper builds on data from the newly established Corpus of American Norwegian Speech and argues in favor of an exoskeletal approach to language mixing. This approach distinguishes between abstract syntactic feature bundles and the morphophonological realization of these bundles, much like in late insertion approaches to morphology. A main goal of the paper is to show how the word-internal mixing patterns observed in American Norwegian can be analyzed in a model of grammar employing an exoskeletal approach with late-insertion.