Although open educational resources (OERs) can help bridge high school-university vocabulary gaps, central questions remain unanswered regarding effective design that enables students to go beyond the "small chunks" that typically characterize vocabulary learning in mobile learning environments (MLEs). This bi-national study adopted a design-based research paradigm to collect input of students at two Chinese universities regarding design factors to overcome potential barriers to learning vocabulary in MLEs. The study iterated through a cycle of analysis, development, implementation, and evaluation with two cohorts of 222 and 136 students, respectively, over two years. Results showed that L1 translations correlated with significantly improved performance on basic-level vocabulary exercises and pop vocabulary quizzes. However, results suggest that moving mobile learning into the mainstream will require designing more effective scaffolding for complex vocabulary learning as well as clearer guidelines for optimal integration of PC and MLEs for supporting self-directed vocabulary study.