Under an EU code of conduct, the three companies report routinely on their efforts to stop election interference. Facebook, for one, has been criticized for being a tool for foreign interference in elections.
Tuesday's reports say Facebook, Google and Twitter are tightening advertising policy and surveillance, particularly with election-targeted ads.
But the commission urges them to share fake account data with outside experts and researchers.
Millions of people across the 28-nation bloc will vote in the May 23-26 European Parliament elections.
Polls show nationalist and populist parties could make significant gains, while mainstream parties would lose seats but retain control over the assembly.