There are plenty of opportunities if you take advantage of them. While the school itself is located in a wealthy suburban area, Pontiac is close by where the median household income is around $27,000. One night a month, OUWB students staff the Gary Burnstein clinic, which provides healthcare to underserved community members. The sign up usually fills quickly because it's an amazing experience.
OUWB students also started an after school program called "score for success" at a middle school in a neighboring community that has a large immigrant population. During the program, students help the middle school students with their homework and literacy by reading with them. After that, everyone goes to the gym to play a sports game with the middle schoolers (soccer, volleyball, basketball).
OUWB also offers a lot of service days throughout the year (such as on MLK Jr. Day). For these days, OUWB finds service activities throughout local communities for students to sign up to participate in. A lot of the organizations provide services and resources to underserved. Activities can include cooking a meal for a homeless shelter, boxing meals at Forgotten Harvest, sorting medical supplies at an organization that provides surplus supplies to places in need. The list goes on.
A few students recently started a Street Medicine group at OUWB and that should be underway shortly as well.
Lastly, you get a lot of exposure to various organizations that support underserved community members through lectures and various other activities that would be happy to have medical students work with them. For example, the professor for the medical humanities and clinical bioethics course is on the board of a local warming shelter (HOPE) which also has a recuperative care center as well. Through the course you get to go to the center and learn more about it and they are always willing to take students to volunteer or help in any capacity. A lot of students work with this particular professor on Embark projects if they are interested in research regarding homeless populations. Embark is the required research project students must complete by the end of their four years.
There are certainly more opportunities that I am forgetting but moral of the story is that the opportunities are available to work with underserved near the school and if there isn't one that specifically targets what you want you have the chance to start one.