I cook a few meals ahead. That way I only have to reheat. I don't like food laying around too long, so I freeze some. I've done chili, roast beef, vegetable soups, chicken corn soup. Soups are simply thaw and reheat. The roast beef I froze in a small container. A package of instant potatoes and a veggie makes a quick meal. You can have the beef just so, or hot beef sandwiches, beef and gravy over noodles... Lots of possibilities.
Whatever hits the fan will not be evenly distributed.
I have little experience with bears, but lots of experience as a cook. You can get the same effect as a crockpot in terms of convenience and efficiency by going to a pressure cooker. Cuisinart makes an excellent, SAFE, electric-powered pressure cooker. It means that you'll be putting your meal together at the end of the day rather than at the beginning, but the cooking happens very fast. We take ours with us in our rig. In fact, we're taking ours to Yellowstone next week. I like it because it gets the cooking out of the RV. I've been using it at home this week to avoid heating up the kitchen. I made a lemon cheesecake in it yesterday :-). Hope this helps!
If you run the crockpot during the day, while you sightsee, I would feel quite safe. The CG at Yellowstone is always crowded with campers; I think it'd be quite unusual to have bears wandering through in the daylight. And if they did the on-site rangers would do their best to shoo them off.
I don't think you would have a problem. To be on the safe side make sure you don't have anything extra plugged in or on. Sometimes when I use my toaster oven and I have something else plugged in it will trip the breaker. It doesn't do any damaged by any means, but you might come home to a cold crockpot.
I have to agree with sbmowrey. If it's that scary for some to have a crockpot in Yellowstone imagine what it's like for someone backpacking that might have a sandwich. I can hear the bears trampling their way through the thickets just to get some PB&J.
In the wilderness, a bear will travel a great distance to get at a PB&J.
Many years ago, I was backpacking out of the cottonwood lakes/new army pass region of the southern Sierra. I camped just south of the intersection with the John Muir trail, put all my SEALED food in a bag and hung it from a tree, and went to sleep. I'd been hiking all day and I was dead tired.
A couple hours later I awoke to the sound of an enormous Black Bear ("enormous" for a Blackie) calmy chewing its way through my food. Since in California the only Blackie ever to kill a human was a captive movie bear, I took two pots and started banging them, and actually walked up until I was banging them right in his/her ear (not a good idea, and I will never do that again). The bear did not even look up. Turns out this area was a dumping ground for unruly bears from Yosemite, and this was a professional moocher.
In the morning, not one package of food did not have huge fang marks in it, and ugly saliva like tapioca. Turns out the bear was attracted to my packaged lemonade mixes, which in manufacturing left a minute amount of sweet/tart lemonade mix on the outside. These things were tiny and the bear had ripped each one open.
So, go ahead and mock the "hand wringers" who will not give a wandering bear any reason to select their campsite. Darwin will have his last laugh, no matter what the cost.