I've decided that oatmeal is not the best bedding, at least for the beetles. I haven't thought of any way to take the beetles out of the bedding with its (hopefully!) eggs in it, other than picking them out a few at a time. Since the oatmeal is close to the same size as a beetle, I don't know what kind of sifter I could use.
I found out that I could buy a 25 pound bag of wheat bran at Tractor Supply for just over $6.00.....and that's BIG bag! It's fine enough that I'll be able to sift the beetles out. (I still have to find a sifter that will let the beetles through.) I did read that sometimes there are grain mites in some bedding, so I microwaved a bowl of it for two minutes, hoping that will kill any mites.
Then, I picked out all my beetles to move them to the new bedding. And then I dumped the old oatmeal they had been living in (and hopefully more eggs) into the bottom tray which held the original worms along with the last oatmeal I separated the beetles from. I had about 20 worms left in that bin and they're probably not far from pupating, so I moved them into the pupa bin.
I've looked closely at the stuff in the bottom of that bottom bin, but can't tell that anything looks like an egg or a baby worm. :=(
I'm showing a picture of the beetles in their new bedding with some pieces of cauliflower core.