According to this list, there are 16 members of Congress who were "out" while in office. All served in the House of Representatives, although one also served in the Senate. Of these 16, 4 are Jews (25%), including the only Senator (Frank and Polis are full, Cicilline is half, and Baldwin is a quarter).
During the time period that the gay ones have served -- the 1970s through today -- Jews have made up between 5-10% of the House. They are therefore 2 or 3 times over-represented among those members of Congress who are gay.
Or at least those who are openly gay -- we'd need a more exhaustive and reliable list of who was in the closet, and check them by ethnic background. Being 2-to-3 times over-represented doesn't seem like it'll go away even if Jews were less likely to be in the closet, and we counted both closeted and open homos. At any rate, they'd still be more likely to be open about it, i.e. to make it one of the issues on their agenda.
Related post: Jews are more than twice as likely to be gay, though equally likely to be lesbian.