Cooking any sort of white meat, turkey or chicken in a slow cooker will only result is tough stringy meat.
Put a sliced onion, a couple of stalks of sliced celery, some chopped parsley your salted and peppered half turkey breast in an oven safe roasting pan. Preheat your oven to 425 and put your turkey breast into the oven for 20 minutes, add your quartered red potatoes and 1/4 cup of dry white wine, put on the lid of the pan and continue to roast for another 45 to 50 minutes. Test with either a meat thermometer to see if it has reached 155 to 160 degrees or when poked with a fork the juice runs clear, not pink.
Remove and let sit for 20 minutes or so while you make a salad.....remove and slice your turkey breast.

I agree, never in the crockpot! I either bake it partially covered at 325-350 for 1.25 hours or until the thermometer reads done or I cook it on the grill.

Linda and Compumom: 325-350 for 75 min, or 425 for 20+45-50 min. Now I'm even more confused! I've eaten turkey breasts cooked in the crockpot, and also chicken, and they didn't turn out tough and stringy - actually they were juicy and delicious. But I've never done a small half-breast of turkey this size, and that's what I want to do since it's going to be over 100F tomorrow and I don't want to turn on the oven.

I agree with antiejen and Bumblebeez, turkey breast cooked in a crockpot definitely does not result in "tough stringy meat." Every bit of chicken or turkey I have eaten that is cooked in a crockpot is very tender and juicy. If others' results were tough and stringy, it was because the poultry was cooked incorrectly in the crockpot.

Cook on low, 6 hours. My crock pot does run hot, but that has worked for me. Mine has low, med and high settings.

Well, I ran out of time yesterday to cook it in the crock pot, so I ended up roasting it in the conventional oven. First of all I should point out that the breast weighed 1.75#, not the 2.75# I gave in my initial post.

Anyway, here's what I did:

I followed Linda's guidelines (thank you, Linda) but at Compumom's temperature (350F). In a large roasting dish, I placed the half-breast on a nest of thinly-sliced onion (1 large onion) and several peeled garlic gloves. I seasoned the breast with S&P and I few other savory seasonings I like, topped with a several dots of butter over the skin, and popped the dish in the fridge until ready to heat up the oven.

Meanwhile, I cut 3 large (the size of baseballs!) red potatoes into chunks tossed them with a little olive oil and dried rosemary - just enough oil to lightly coat the potato pieces

At baking time, I poured 1/4C dry white wine and about as much chicken broth (both at room temp) around the breast (not over it) and placed the potatoes in the bottom of the dish around the breast. Covered loosely with a foil tent and baked about 1.5 hours (I checked after 1.25 hours but not quite done). Removed from oven when temp reached 165F with instant-read thermometer, let sit 10-15 minutes with foil tent.

The meat was extremely juicy and tender. The thin slices of onion caramelized in the wine/broth/juices and created a delicious sauce for the potatoes - as well as being tasty to eat. (There were a few thicker slices that didn't caramelize; next time I'll be sure ALL the slices are thin - they'd also be a nice addition to a turkey sandwich the next day.) Next time I may add a bit more liquid to create a bit more juice, but really it was fine as is.

I still maintain it's possible to make a juicy tender delicious turkey/chicken breast in the crock pot --- if done correctly --- and I plan to give that a whirl sometime soon. I've found several recipes on-line with very favorable reviews to indicate they are worth trying.

Thank you all for your suggestions and input!

PS - I wanted to add brussels sprouts (halved) with the potatoes but was afraid this would increase cooking time. Will that work, all together in the same dish at the same time? The potatoes went in with the turkey and all turned out fine.

I'm not much of a cook, but I've roasted lots of chickens and turkeys, including just the breast.
The juiciest is when I do it in my slow cooker. Literally fall apart tender. I rarely roast these days because I just can't get it that tender in my oven.
What I do is make a bed of carrots (I don't care for onions), season the poultry very well, put it on top of the carrots, and cook on high about 4-5 hours (mine doesn't get that hot), that's it.

Comes out perfect every time.