To make stuffed acorn squash, you only have to rinse the squash, cut it in half lengthwise and scoop out the seeds. Easy! To cook it, we're roasting it in the oven: Place the squash cut side down on a lightly greased baking sheet, then bake it for around 30 minutes. It may not have quite cooked through by then, but that's fine because it will bake for another 5 minutes with the filling.