Online surveys have been preferred to assess needs during the COVID-19 pandemic. However, pandemic disruptions and disparities among socially vulnerable groups may affect online survey participation. Using data from the Fostering Food Security, Health, and Resilience in Graduate Education (FORGE) survey of graduate students (Nov-Dec 2020), we developed survey participation metrics: overall response rate, percentage of questions answered, time spent responding, and response to open-ended questions. Nonparametric tests identified differences in participation associated with demographics, food or housing insecurity, or mental or physical health. The response rate (21%) was comparable to a pre-pandemic online survey, with demographics similar to total enrollment. Minority students discontinued the survey earlier than white students, answering fewer questions (p< 0.01). Non-gender conforming students and those experiencing insecurity or poor mental or physical health took more time responding (all p< 0.05). Providing open-ended responses also varied by demographics, insecurity, and health status. Social vulnerability can affect online survey participation, potentially biasing estimates.