- O castelo da bruxa confusa
- O mundo mágico dos números
- O Pequeno Livro dos Números: Vol. 1
- O Pequeno Livro dos Números: Vol. 2
- O Pequeno Livro dos Números: Vol. 3
- O Pequeno Livro dos Números: Vol. 4
- O porco mais elegante do mundo
- O sonho de Dam-Dam e do sr. Gom-Gom
- Ocean Counting
- Octopuses One to Ten
- On the First Day of Kindergarten
- On the Job: Vet Comparing Groups
- On the Job: Vet: Comparing Groups: Read-along ebook
- One Big Pair of Underwear
- One Bright Ring
- One Clucky Hen
- One Dark Bird
- One Family
- One Fish Two Fish Red Fish Blue Fish
- One Fish Two Fish Red Fish Blue Fish: Read & Listen Edition
- One Fish, Two Fish, Red Fish, Blue Fish
- One Foot, Two Feet
- One Fox
- One Golden Rule at School
- One Hundred Hungry Ants
- One Hundred Shoes
- One Is a Lot (Except When It's Not)
- One Leaf, Two Leaves, Count with Me!
- One Little Lot
- One Little Monster
- One Little Piggy: Counting Books for Toddlers
- One Naked Baby
- One Potato, Two Potato
- One Some Many
- One Tractor
- One Two That's My Shoe
- ONE Very Big Bear
- One White Rabbit: A Counting Book
- ONE Very Big Bear
- One White Rabbit: A Counting Book
- One, Two, Buckle My Shoe
- One, Two, Three
- Onka Yoruba: My First Naija Numbers
- Os dez gatinhos
- Os filhotes do vovô coruja
- Os números
- Oscar
- Our Family Reunion
- Our Favorites
- Our Harvest Lunch
- Our Trip to the City
- Our Vacation Budget
- Outer Space 123 Count With Me
- Over in the Grasslands
- Over in the Jungle
- Over in the Ocean