General figures indicate stark differences between both cross-country and cross-party groups in MEPs’ activity. Our attempt to explain this variation accounts for five variables (plus age for control): (1) the background of the MEPs, (2) their political experience, (3) belonging to a European party group, (4) the duration of their mandate, and (5) their status (i.e. elected versus appointed). Using statistical techniques and original data, we focus on the representatives coming from the most recent EU member state (i.e. Romania) as activity differences are most likely to occur at their level. Results indicate that, in essence, the socialization with the EP workings (duration of term in office) considerably shapes newcomers’ performance.