Slow Cooker Cream of Broccoli Soup

1 tablespoon vegetable oil

1 small onion, chopped

2 (10 ounce) packages frozen chopped broccoli, thawed

2 (10.75 ounce) cans cream of celery soup

1 (10.75 ounce) can condensed cream of mushroom soup

1 cup shredded American cheese

2 (10.75 ounce) cans milk

Heat vegetable oil in a large pot over medium heat; cook the onion in the hot oil until soft, 5 to 7 minutes.

Drain as much liquid from the onion as possible. Transfer the drained onion to a slow cooker.

Place the broccoli, cream of celery soup, cream of mushroom soup, American cheese, and milk into the slow cooker.

Cook on Low until the broccoli is tender and the flavors meld, 3 to 4 hours.