Mexican Soup

This is a recipe given to me by my daughter, and I believe she received it from her mother-in-law. I just know it is delicious.

2 lbs. ground beef
1 chopped onion
Brown together and drain off fat.
Add:
1 can Rotel tomatoes and green chilies
2 cans chopped tomatoes
1 tsp. salt
1 tsp. pepper
1 pkg. Taco seasoning
1 pkg. Ranch dressing mix
1 can pinto beans
1 can chili beans
1 1/2 cups water
1 can whole kernel corn
Bring to a boil. Lower heat and simmer for awhile.