I think you know the answer, which is why you
decided it was noteworthy. This size of prey is probably not normal, but
then not so weird either. Although I regularly (eg once or twice a week) or
occasionally eat a lot more than I normally do, too.
I think I recall years ago, an article in Aust Bird Watcher of their
predation on Sugar Gliders. Oops, just as well I checked, I got that wrong, it
seemed a bit extreme, it was Feathertail Gliders and it was Rowley 1989 in ABW
13:126, as revealed in HANZAB V6 that I have just looked up, and yes there are
other records of lizards in their diet.
And yes it is a skink. Too many
possibilities for me to guess at which one.