This chapter examines corpus data from learners of English as a Foreign Language in order to test if there is evidence for (1) cross-linguistic influence, (2) universal processes of Second Language Acquisition (i.e. simplification or overgeneralization) and (3) interaction between the two. SLA research has long approached cross-linguistic influence and universal processes as distinct and mutually exclusive phenomena. More recent work has begun to acknowledge the interaction between them, but this has not been examined through more extensive corpus evidence. This study probes the notion of universal processes of SLA through the examination of L1-induced quantitative and qualitative differences behind features that appear similar on the surface. The focus is on two morphosyntactic features, embedded inversion and omission of prepositions, which have been identified as commonly occurring features in non-native Englishes. While the results show joint tendencies between different L1 populations, we find no evidence for invariant universal features; the higher frequency and distinctive nature of these features amongst learner groups with a trigger in the L1 point to strong L1 effects. The discussion highlights issues of definition and the benefits of bringing together SLA theory, learner corpus evidence, and findings and insights from research into L2 varieties of English.