We describe Group-Advantaged Training of Research (GATOR), a yearlong structured program at the University of Florida that guided graduate student mentors and their undergraduate mentees through the mentored research process. Using the national Survey of Undergraduate Research Experiences for an academic year, we found that outcomes for our mentees were similar to those for other programs. We also used an internal survey, combined with qualitative observations, to develop a road map of the mentoring process, which we call the "Metamorphosis of Mentorship." This model provides tangible steps on the road to becoming a scientist, incorporates reasons mentees stall in research, and suggests ways to overcome mentoring challenges and prevent attrition. The structure and outcomes of this program will be useful to researchers and administrators working to engage undergraduates in scientific research, particularly at large universities where undergraduates are often mentored by graduate students.