Among the smallest of the herbivore-omnivore species, Othnielosaurus stand roughly waist height to an adult human, and weigh only about as much as a bag of sugar. For this reason they have now become one of the most commonly experimented with species on the island. Many variations on the species appear together due to dozens of appearance experiments over the years.

Like other similar species they are bipedal and fast runners, preferring the leaves and fruits of bushes rather than always bending over or reaching up. Occasionally the species has been known to dine on insects, snails, and small lizards. They travel in family groups but will scatter if disturbed instead of grouping together for defense.