Melons or anything melon like. Can't say if they get fat, but it's the only food I've see where you can even see the worm tracks where they have plowed through hehe.

Horse manure.

pumpkin

My guys go crazy for moistened, plain oatmeal.

reedandleaf are you talking Quaker Oats raw or cooked?

Mine love pumpkin and melon.

Raw, soaked in room-temp water until the oats are nice and moist.

I get the oats in bulk from a great local co-op. This is a much cheaper option than buying name brand oatmeal (and cheap is good seeing as I don't even eat oatmeal myself, I'm just getting it for the worms!) And also, I can be sure that the co-op bulk oatmeal doesn't have the added salt, flavors, or sweeteners that brand name oatmeal often contains.

When I put it in the bin, I bury it roughly two inches down. I spread it thinly in narrow furrows because, not being a porous substance, it can go anaerobic if it is placed in too thickly. I would guess I spread it about 1/2 of an inch thick by 1 and 1/2 -2 inches wide by 6 inches long, in several locations around the bin.

They go absolutely nuts for it. They don't touch any other food in the bin until all of the oatmeal is gone, it gets eaten up in the blink of an eye, and when I give it to them I don't see them for days--they're too busy working hard. If I dig in the bedding to check on them, they are all glommed up in mass worm/oatmeal balls of ecstasy :)

I know it probably sounds silly that I buy oatmeal just for the worms, but they love it and they work so hard for me, I like to spoil them sometimes-- who would have thought that worms could be so darn cute!

Reedandleaf, I tried the oatmeal and the worms love it. Wanted to start a second bin and the worms from my bottom bin came up to the top bin like crazy.

Thanks to everyone for your information my worm family like all of your suggestions!

Rotten cucumbers, without a doubt. I also still have some Purina worm chow left over from a 50lb sack I bought years ago for around 8 bucks, and that works well. But, if you want to fatten them for fishing or whatever here's a recipe from my friends over at the Happy D worm ranch.
http://www.happydranch.com/wmfat.html

WORM FATTENER RECIPE

5 parts chicken layer pellets or chick starter
2 parts wheat or rice bran
2 parts alfalfa pellets
1 part whole wheat flour
1 part agricultural lime
1 part powdered milk

Mix several handfuls with food waste before feeding to worms. Worm Fattener is very dry & must be moistened so the worms will consume it.

Cornbread. Though too much will heat up the bin.