Move the oven rack to the middle position. Heat the oven to 400°F.
Cut the potatoes into 6-8 wedges each and place the wedges into a large bowl. Zest one of the lemons into the bowl with the potatoes. Juice 2 lemons through a strainer and into the bowl with the potatoes. Add the 1/3 cup olive oil to the bowl with the potatoes and toss well.
Add the 2 cloves garlic, 2 teaspoons salt, 1 teaspoon dried oregano, and 1/2 teaspoon freshly ground black pepper to the bowl with the potatoes. Toss again to distribute the seasonings.
Transfer the potatoes to a 9x13" glass or ceramic baking dish, or similar-sized casserole dish (avoid using a metal baking pan, as it can react with the lemon juice). Pour the 3 cups chicken stock over the potatoes (it will look like a lot of liquid - don't worry, it will be absorbed/evaporate). Bake until the potatoes are soft, the edges are starting to brown, and most of the liquid has been absorbed (about 75-90 minutes), stirring the potatoes gently every 15-20 minutes.