Some of these I know may be more on your horizon but I think they're under-read so I included them too.
These are at varying reading levels but I would estimate that I read these all in the younger elementary grades.
So, to repeat, these are all great books and in my opinion if a children's book is really great it is not only enjoyable for a kid but also for an adult and all of these I continue to re-read even though now I'm a "grown up".
- Maud Hart Lovelace- Wrote the Betsy-Tacy series
- Sydney Taylor- Wrote the All-of-a-Kind Family series
- Carolyn Haywood- Wrote the B is for Betsy books
- Lloyd Alexander- Wrote the Chronicles of Prydain
- Betty MacDonald- Wrote the Mrs. Piggy-Wiggle series
- Michael Bond- Wrote A Bear Called Paddington series
- Arleta Richardson- Wrote the In Grandma's Attic series
- A.A. Milne- Wrote the Winnie the Pooh series
- Walter R. Brooks- Wrote the Freddy the Pig series
- Thornton Burgess- Wrote Old Mother West Wind and others