I just made a Turkey meatloaf, using a standard recipe that usually turns out good with ground beef, but it was too dry - any help would be appreciated.
Avery's "fattest turkey" advice is solid. I try to find ground turkey breast as opposed to ground turkey, no matter what I plan to do with it, because it's easier to keep it from drying out in various recipes. As he said, ground turkey is so easy to overcook.
You could always add some moisture by throwing some bacon grease into the mix, which I have done in the past with regular (ground beef) meatloaf to help make it as unhealthy and delicious as possible. This should effectively counter the health benefits of using ground turkey over ground beef, but boy is it good!
When my mom makes turkey burgers for the grill, she adds some italian dressing into the mix and swears that it helps keep the burgers from drying out fast. Haven't tried it myself, but I can see how the oil (and water and vinegar, but moreso the oil) would help. It will likely affect the taste of the dish...but that isn't always a bad thing, as I find ground turkey to be significantly more "boring" tasting by itself than ground beef is by itself, probably because of the lack of fat.
My mom's meatloaf recipe included a couple slices of bread that had been soaked in milk and then blenderized with the egg before mixing in to the meat. The milk obviously provides moisture, and the bread a nice carbohydrate matrix to hold onto that moisture. Give that a shot, I bet it will hydrate your turkey. (Do you dare take meatloaf advice from a 25 year vegetarian?)
It's best to use the fattest ground turkey you can find if you are worried about moisture. Don't use the extra lean grinds as fat helps keep the meatloaf moist. If you can find a mixture of ground turkey that is labeled turkey breast or has dark meat in it this will help.
Also, make sure not to overcook the meatloaf as turkey is by far one of the easiest meats to overcook. Internal temperature should read 160-165 degrees max. But I would pull the loaf at 150 and let it rest until it comes up to temperature, covered with tin foil. Almost all cooked proteins will "carryover", that is they will continue cooking after it has been removed from the oven.
Adding stock or extra diced onions for moisture in the mixture will help with moisture but can affect the texture and taste of your loaf.
In general, fat in ground meat will keep dishes made with it moist. You can substitute a non-fat liquid (such as stock or tomato juice) for the fat to gain back some of the moisture, but it will change the texture. We've had good results using salsa in our meatloaf, since it provides acidity, vegetables, spice, and liquid. This reduces the amount of egg and other liquid we need. (We're down to one egg for two loaves.)
Another way to deal with the issue is to add more fat, but cook the meatloaf using a double-layered pan with holes in the top layer. (Such as a broiler pan or special meatloaf pan.) This allows some of the fat to drain off, reducing the fat and calories for the meatloaf.
Edited to correct the name from "grilling pan" to "broiler pan."