Cooperative education (co-op) programs in engineering provide students with relevant professional experience before they finish their undergraduate degree. Most programs and employers have academic eligibility requirements that make it difficult to infer whether successful employment outcomes are due to the selection of higher performing students or the causal effect of co-op participation. The goal of this study is to determine factors that are associated with participation in engineering cooperative education programs, controlling for eligibility. Longitudinal and multivariate data from six different institutions, each with large engineering programs where co-op participation is not mandatory, were studied with stepwise logistic regression. Results show that cumulative GPA at the end of the second semester is the strongest predictor of co-op participation. While institutional differences, year of matriculation, ethnicity, major discipline, and high school variables are also significant, gender is not related to co-op participation. The results from this paper will provide useful information for colleges, co-op administrators, and employers about who participates in co-op programs.