Preheat oven 375°F and lightly oil the bottom of two baking dishes (9×13 glass dish works well).
Wash the squash and even the bottom by cutting as little as possible off to level it. Cut the top of the squash off – you can cut it high or low, just be aware that what’s left is the capacity of your bowl, so plan accordingly.
Scrape out the seeds and strings from inside, washing and reserving the seeds for baking, if you like. Either use the squash as is, or use a round biscuit cutter to form an even and uniform circle for the interior of the bowl.
Brush olive oil onto the outside of the squash. Place them into the baking dishes and do not let them touch.
Bake for 30-45 minutes, depending on the thickness of the squash. The inside should be fork tender (do not test the bottom of the squash with the fork, or you could poke through and cause your bowl to leak soup!). The flesh of the squash should be soft enough that you can scoop out some of the inside of the bowl while eating the soup.
Remove to cool slightly before serving with your favorite soup.