I wouldn't try a raw potato....but either a baked potato or dry potato flakes ( instant mashed potatoes) would work.
How long to bake it depends on how cold it is, how hot your oven and what the shape is.
If you make a round loaf....rather than flat...I would cook it for 25 minutes...
But half a pound meat loaf is really very small.
Really I would use an instant read thermometer and begin testing after2 0 minutes....temp should be 160 for a non pink loaf.
Linda C

I have a good friend who is gluten intolerant, so I am always interested in recipes to serve when he and his wife come for dinner. I have never used potatoes. What about oatmeal (rolled oats) instead of crumbs?

bbstx---Celiac patients are cautioned to use only oats that are certified GF because oats are often processed on machinery that also processes wheat. Also, some experts believe that oats themselves are harmful to celiac patients. GF oats can be found in health food stores and also places like co-ops and Whole Foods. It would be wise to ask your friend if he can have oats. Celiac disease and gluten intolerance aren't exactly the same and I have researched only celiac disease.

Lindac---I have tried so many GF foods and substitutes and found so many of them to be awful that I have thrown away a small fortune in food. Not to mention that many GF products are horribly overpriced. If I don't like the meatloaf it will be recycled to my four Siberian huskies. They would love a full pound but I am going to experiment on a small loaf. I live alone so even if I like it, it will last a while. I eat meat often but don't consume large portions at a sitting.

I also have a gluten intolerant friend. I sometimes use cooked rice....cooked very well and mixed in, brown rice.
But as I said, instant mashed potatoes work very well.
Or use no filler....just veggies and egg.
no need to make a trial batch, it works.
When my gluten intolerant friend and her husband come to dinner, I usially make meat...roast or steak or chops, seasoned but I am caareful not to use any spice mixes or prepared marinades as many contain wheat, and usually rice of some sort....either pilaf or risotto and a veggie and salad. Sometimes I make a big pot of soup, but he's not too fond of soup.
Desserts are the challenge...I usually do cheese cake with a nut crust, or flan or a pie and make her filling separate.
But I always make home made bread, because when Momma is gluten intolerant, the rest of the family often doesn't get to eat good bread!
Linda C

Bob's Red Mill has certified GF oatmeal that would work well in meat loaf, as long as you don't have a problem with oats in general.

Other options:
-Crushed rice cakes or crushed crisp rice or corn cereal

-Crumbled cornbread - my mother dried thin slices of her homemade GF cornbread and made "bread" crumbs from them for dredging, etc.

-GF baking mix

-Cream of Rice Cereal

-1/2 c. coconut flour per 1-pound ground beef (see recipe below)

Bake your 1/2-pound meatloaf to an internal temperature of - 160-165°F. (check with an instant read thermometer or a meat thermometer). It will probably take 20-30 minutes.
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Meat Loaf
(source: Cooking with Coconut Flour - by Bruce Fife, N.D.

1/2 c. coconut flour
3 eggs
1 c. finely chopped onion
1/2 c. chopped bell pepper
1 t. salt
1/2 t. black pepper
1/8 t. marjoram
1 pound ground beef
1 16-oz. can tomato sauce

Combine coconut flour, eggs, chopped onion, bell pepper, salt, black pepper, thyme, and marjoram in a bowl. Add ground beef and 1 c. (8-oz.) of tomato sauce and mix well. Shape mixture into a loaf and place into a baking dish. Pour the remaining 1 cup of tomato sauce over the top of the loaf. Bake at 350°F for 1-1/4 hours. Makes 6-8 servings.

-Grainlady

I'm going to a fancy, and ridiculously expensive organic/health food/vitamin and supplement store tomorrow and I will look for coconut flour. I will definitely try it in the meatloaf recipe. Thanks, grainlady. I finally made a decision and ordered a Kitchenaid Artisan 5 quart mixer. I may take up to 9 days to arrive, but heck, the shipping was free. I will have to make a couple GF loaves and freeze them because I have to return my friendÂs mixer soon. She bakes to earn extra money and I feel very uncomfortable keeping her mixer even though she said she didn't need to bake until Wednesday. I have read conflicting opinions regarding the science behind the argument that freezing or refrigerating yeast bread changes the texture. I have left my current loaf, made two days ago, in a zip lock bag on the counter. I am waiting to see how long it takes to get moldy.

I use toasted GF waffles to make "bread" crumbs.