Oak Tom was a jolly fat male squirrel who was once a mischievous Dibbun of Redwall Abbey. He was the husband of Treerose. Tom seemed to have adopted a thief's nature, as when Mother Mellus asked him if he stole a gift he gave her, he pulled a long face. He was an old friend of Rufe Brush, and wrestled with him after he returned to Redwall after seasons of being away. Despite his weight, Oak Tom could perform somersaults and other gymnastics and effectively move around the forest undetected.
Tom discovered oar slaves were held in a cage by corsairs and warned his friends of the upcoming difficulties in freeing them. He eventually assisted Rufe Brush and Treerose in bringing the slaves to the Abbey, while the members of the Long Patrol fought valiantly against Greypatch and his searats.
After the battle, Oak Tom pursued several of the remaining fleeing searats through the forest and killed them one by one in revenge for the deaths of Colonel Clary and Brigadier Thyme.
Later, Oak Tom married Treerose and the pair relocated to Mossflower Woods. After their wedding, he was described as sturdy, suggesting that he may have lost weight at some point. He and Treerose acted like the protectors of the trees, as they traveled around and helped the Redwallers in times of need.