- Our Little Brazilian Cousin
- Our Little Canadian Cousin
- Our Little Cossack Cousin
- Our Little Cuban Cousin
- Our Little Czecho-Slovak Cousin
- Our Little Danish Cousin
- Our Little Dutch Cousin
- Our Little English Cousin
- Our Little Finnish Cousin
- Our Little French Cousin
- Our Little German Cousin
- Our Little Hawaiian Cousin
- Our Little Hindu Cousin
- Our Little Hungarian Cousin
- Our Little Irish Cousin
- Our Little Japanese Cousin
- Our Little Jewish Cousin
- Our Little Korean Cousin
- Our Little Persian Cousin
- Our Little Polish Cousin
- Our Little Porto Rican Cousin
- Our Little Quebec Cousin
- Our Little Roumanian Cousin
- Our Little Russian Cousin
- Our Little Scotch Cousin
- Our Little Servian Cousin
- Our Little Siamese Cousin
- Our Little Swedish Cousin
- Our Little Swiss Cousin
- Our Little Turkish Cousin
- Ourson et les Narecnizi
- Out Of The Silent Planet
- Ourson et les Narecnizi
- Out Of The Silent Planet
- Out of the Wild
- Out Of The Woods 2nd Edition
- Outlaw Princess of Sherwood
- Outrun the Wind
- Outside In
- Over Easy
- Over Sea, Under Stone
- Over the Moon (Scholastic Gold)
- Overworld Chronicles Box Set Books 11-13
- Overworld Chronicles Box Set Books 5-7
- Overworld Chronicles Box Set Books 8-10
- Ozland (The Everland Trilogy, Book 3)
- Ozma of Oz