This robust frog may be brown, reddish-brown or red above with a variable number of large, black spots and blotches on the back, sides, and legs. The spots are usually irregular-shaped, with indistinct edges and light centers. The skin on back and sides is often covered with small bumps and tubercles. The eyes are upturned. The lower abdomen and the undersides of the hind legs are usually colored by a reddish-orange or salmon-colored pigment that appears as though it has been painted on (Leonard et al. 1993; Nussbaum 1984; Stebbins 1985). Oregon spotted frogs have relatively short hind legs and extensive webbing between the toes of the hind feet. Sexually mature females range between 60 and 100 mm snout-vent length and males range between 45 and 75 mm (Licht 1975).
 
Since nearly the time of its original description in 1853, the systematics of the "Western Spotted Frog" group has been a source of both confusion and debate. In 1996, however, a team led by David M. Green published the results of a study on the genetics of Spotted Frogs and concluded that the group actually contained two "sibling" species-the Oregon Spotted Frog and the Columbia Spotted Frog (Green et al. 1996 1997) . The decision to "split" the species was based upon the results of laboratory studies that indicated significant genetic differences, despite a lack of reliable morphological differences. Because the two species have allopatric ranges, they may be reliably identified based upon the location where a frog is encountered.

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