Two-year community college (CC) students face many barriers for recruitment and retention into Science, Technology, Engineering, and Math (STEM) fields and vertical transfer to 4-year universities (4YUs). Experiential learning, mentoring, and cohort building are effective mechanisms for increasing STEM recruitment and retention, and close collaborations between CCs and 4YUs leverage complementary opportunities, supporting vertical transfer. We present a case study incorporating these concepts for a year-long Geoscience Education and Outreach Program (GEOP), a collaboration among a CC, a 4YU, and a non-profit science center, where 20 CC students participated in integrated academic, research, and internship components over three years. We present program design, implementation, revision, and outcomes for both students and institutions. Cohort-building activities encouraged professional conversations and built peer connections that addressed imposter syndrome, cultural divides, and other personal barriers to vertical transfer. The academic component had the highest completion rate, and a majority of respondents in exit interviews reported the internship as the most valuable experience, with half naming research or aspects thereof as most valuable. The vertical transfer exceeded typical CC rates, with 70% of GEOP students transferring to a 4YU, all in STEM disciplines. Successful implementation of GEOP required multi-institutional coordination, effective mentor-mentor and mentor-student communication, and program flexibility. Based upon our experiences, we provide several recommendations for implementation of similar programs.