>>Okay, here's the issue...my 2 year old Corgi (adopted from rescue at 8 months) will NOT poop in the backyard (grassy, fenced, with a doggy door that allows her all-day access). She gets walked twice a day (our other dog, a beagle, does poop in the yard and gets walked only once a day).
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>>Not that we MIND walking but when schedules are tight we will have a dog walker come, just so she can stick to her routine. Frankly, we'd love to do without the extra expense, and, would love to have the option of shorter or fewer walks in the middle of blizzards and the like.
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>>Is there a way to teach a dog to poop on command, or is that even the right approach? Common sense tells us that, as she has NEVER had an accident in the house since the first day she was here, if we just didn't walk her one day she would eventually figure out what to do (we assume she is peeing in the yard, though we've never actually SEEN her do it). But we haven't tried the cold turkey approach for fear she would be confused about what to do. Ideas?
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No need to go cold turkey. Associate a phrase with relieving herself on walks, cuing her with that phrase when she is about to go and praising her with that phrase when she has eliminated. Then try using that phrase at home. Be gentle, and when she finally goes in the yard once, praise.
She may have been punished in the past over housetraining, and as a result be shy about doing it in front of a person. Praise and reward helps overcome this.
Also, if you are not picking up the poop on walks, begin doing that. You can put some of it in the yard to encourage her to eliminate there. Also the very fact of you picking it up sends her a subtle message that a walk is not the place for it, without scolding.
The plastic bag method makes pick up easy. Put a plastic bag such as a produce bag from the grocery store over your hand like a glove. Pick up the poop with that glove, and then turn the bag inside out around the mess. Tie the top and it will be a tidy package to carry home.
Don't scold her when you pick up. Just do it calmly and quickly and get right back to the walk. Before and after every single walk, take your dog to the yard off-leash (if you have a fence) and encourage her to potty there. One day she will surprise you by doing so.
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Kathy Diamond Davis, author, "Therapy Dogs: Training Your Dog to Reach Others," 2nd edition, and the free Canine Behavior Series articles at http://www.veterinarypartner.com/Content.plx?P=SRC&S=1&SourceID=47
Of course it was always followed by lots of praise. 
