This chapter examines several syntactic properties that have been explored in heritage grammars, from the knowledge of A- and A-bar dependencies to binding to word order. If we set aside problems in production, the syntactic behavior of heritage languages seems remarkably rational. Heritage languages differ from the baseline in a number of ways, but their syntax does not bring unexpected surprises that would call for a radical reconceptualization of existing syntactic tools or syntactic theory. This means that heritage speakers build their grammars following universal principles of language design. In accounting for the differences between baseline syntax and heritage syntax, researchers often rely on processing considerations, shallow processing in particular. This chapter argues that processing may constitute the starting point for grammatical rearrangement but cannot account for changes in heritage grammars all by itself. Instead, grammatical representations change based on the restructuring of oppositions present in the baseline and adherence to the least complex structural option available in a given context.