Brownies are meant to be crisp on the outside and soft and fudgy on the inside. There's a difference, though, between deliciously soft and downright mushy. If your brownies are too soft, the problem is likely due to improper cooking times or temperatures. You probably need to make a few minor adjustments to get it right.
Cooking Time and Temperature
A common problem when baking brownies is that the outer edges get too dark before the middle of the pan is done. To correct this problem, turn the heat down by 25 degrees, especially if you're using glass or dark aluminum pans. You should also reduce the oven temperature by 25 degrees if you're using convection cooking. Try draping a one-inch collar of aluminum foil around the outside edges to slow browning. If necessary, increase baking time an additional five to 10 minutes to allow the middle to set. Check the brownies frequently so you don't dry them out by overcooking.
Doneness
Set the timer for about 10 minutes before the suggested time so you don't burn the brownies. To test for doneness, insert a toothpick in the center of the pan of brownies. If the toothpick comes out wet, the brownies aren't done. If it comes out dry, they might be overdone. When done, the toothpick should have small fudgy morsels on it.
Storage
Another reason brownies might be too moist in the middle is because you're cutting them too soon. It's tempting to dig right in, but set the pan on a cooling rack and wait for at least two to four hours before cutting brownies. When cool, the brownies harden slightly and also taste better. Once completely cooled, cut the brownies into bars and store the bars in an air-tight container. Use them within two days or freeze them for up to three months.
Ingredients
It's possible that even with all these adjustments, your brownies are still too moist in the middle. Perhaps you prefer a drier brownie, rather than the dense classic recipe. If so, add another egg and reduce the oil or butter slightly, which will result in a cake-like brownie that is light, rather than thick. If you're using a mix, read the package directions, which usually offer suggestions for making cake brownies.