In a large pot over medium heat, add in the olive oil. Next, add in the onions, garlic, celery, and peppers and saute for 4 to 6 minutes or until lightly browned.
Transfer the shellfish to the cioppino stew and mix in. Next, add the shrimp and the crab legs and cook for 2 to 3 minutes and then add in the squid and cook for 1 to 2 more minutes or until done.