This study documents knowledge of UG-mediated aspects of optionality in word order in the second language (L2) German of advanced English and Japanese speakers (n = 39). A bimodal grammaticality judgement task, which controlled for context and intonation, was administered to probe judgements on a set of scrambling, topicalization and remnant movement constructions. Given first language (L1) differences and Poverty of the Stimulus, English and Japanese learners face distinct learnability challenges. Assuming Minimalist grammatical architecture (Chomsky, 1995), convergence on the target language would entail the unimpaired availability of Universal Grammar (UG), i.e., computational principles and functional features beyond their L1 nstantiation. Irrespective of L1, the L2 groups are found to establish systematic native-like relative distinctions. In addition, L1 transfer effects are attested for judgements on scrambling. It is argued that these findings imply that interlanguage grammars are fully UG constrained, whilst initially informed by L1 properties.