Greek and Spanish are two languages that display a similar subject distribution with unergative/unaccusative verbs, but different word orders with focused subjects (SV in Greek and VS in Spanish). Here we consider subject-verb word order in second language (L2) Greek and L2 Spanish in order to test the Interface Hypothesis (IH). To this end, we report a word-order selection task, with a Greek and a Spanish version. The two versions of the task were administered to L2 intermediate and advanced learners and native speakers of Greek and Spanish. The results show that the first language (L1) Spanish learners of Greek approximated more closely native word orders than the L1 Greek learners of Spanish. For the Spanish learners of Greek, the advanced group performed at ceiling, while the intermediate group performed native-like only with unergatives in neutral and direct interrogative subject-focused contexts. On the other hand, for the Greek learners of Spanish, the intermediate group failed in all contexts, while the advanced group performed native-like with unaccusatives in neutral contexts. This asymmetry between L2 Greek and L2 Spanish reveals that the L1-L2 combination determines the learners' performance, and this is unexpected under the IH.