This study examined word order preferences as a function of phrasal length in Basque. Basque is an OV-language with flexible sentence word order and rich verb agreement. Contrary to the universal short-before-long preference predicted by availability models, Hawkins has argued that short-before-long orders are preferred in VO-languages such as English, whereas long-beforeshort orders are preferred in OV-languages such as Japanese (Hawkins, 2004). However, it is unclear how length affects word order preferences when an OV-language has rich verb agreement and allows postverbal arguments. We found a general long-before-short preference, and a tendency to place the verb in a sentence-medial position when one constituent is long. We argue that since agreement morphology signals the thematic role and case of surrounding phrases, it contributes to speeding up sentence processing. We conclude that morphologically rich languages employ both general adjacency mechanisms and language-specific resources to enhance language efficiency.