From the Batcave: Squire and Knight
Technically Beryl was created during Morrison's JLA run, but I think that she became a bit more well known in the pages of Batman. Her "communication powers" also got eventually downplayed (or removed entirely) so I feel like she is definitely more of a Batman character than JLA's. Her appearances in Morrison's JLA and Batman are obviously must reads for any fan of Morrison, but is there anything else worth checking out? There was Knight and Squire miniseries by Cornell and Hodgkins. It fleshes out their partnership and tries to expand DC universe in UK by introducing (and re-introducing) various characters. Nothing spectacular, but solid stuff and it is not like we can be very picky for content with Beryl. After that there was a guest appearance in Batgirl #22. Again, nothing spectacular, but solid stuff that is worth checking out. As a bonus it works as a set-up for Stephanie getting involved with Spyral in Morrison's Batman Inc. storyline. A bit of a side ...