The bake time for a 9x13 yellow sheet cake can vary depending on the recipe and the specific oven. However, as a general guideline, you can expect a 9x13 sheet cake to bake for approximately 25 to 35 minutes at a temperature of 350°F. It's always recommended to start checking for doneness around the 25-minute mark and continue baking until a toothpick inserted into the center of the cake comes out clean or with a few moist crumbs.