One of the best ways to avoid a watery squash casserole is to choose the right squash. Look for a firm, dry squash that is free of blemishes or bruises. Avoid squash that is soft or has a lot of moisture on the surface.
Once you have your squash, cut it into cubes or slices that are about 1-inch thick. If the squash is too thick, it will take longer to cook and may release too much water. If it is too thin, it will cook too quickly and may become mushy.
After cutting the squash, cook it in boiling water for 3-5 minutes. This will help to release some of the water from the squash and make it less likely to get watery when baked.
After boiling the squash, drain it well and then add it to your casserole dish. Be sure to add other ingredients that will help to absorb the water, such as bread crumbs, rice, or pasta.
Bake the casserole at a high temperature, such as 375 degrees Fahrenheit, for 30-40 minutes. This will help the water to evaporate and will result in a less watery casserole.