Edible Uses:
Berries of creeping mahonia are very sour but edible when fully ripe. As with other mahonias that produce fine large berries, creeping oregon grape has been used to make apple-mahonia jelly, wines, pies, and the flowers make an excellent lemonade substitute. The berries are produced in substantial numbers, blue with a white dusting. They are edible after a frost or two which increases their fructose content and decreases their pectin content. Early European settlers and Native People used the berry for food. The fruit has a strong, distinctive flavor, but is not edible until frozen in autumn. While berries are still green in summer, they are mildly toxic, though mainly the potentially toxic alkaloids are present in the leaves and stems. There is no case of toxic response in humans eating the berries, though this may be partly because they are unpalatable until they are fully ripe and been through a freeze or two, by which time they are tasty and perfectly safe. The berries are also high in Vitamin C and have often been used to treat scurvy.

Caution:
Creeping mahonia contains the alkaloids berberine and oxyacanthin. These compounds are present throughout leaves and stems, and are toxic to cattle. A rash to human skin may occur from spines on the leaves.

Medicinal Uses:
The root and root bark have agents that are pain-relieving, antiseptic, laxative, fever-reducing, tonic, that gradually restore health, increase bile flow to the intestines, tend to purify and cleanse the blood, induce urination, and that induce the removal (coughing up) of mucous secretions from the lungs. It improves the digestion and absorption and is taken internally in the treatment of coughs, fevers, psoriasis, syphilis, hemorrhages, stomach complaints, kidney problems and impure blood conditions.
It is the rootstock's healing qualities which made it prized by native people who crushed and dried the yellow roots to cure a wide variety of ailments like ulcers, heartburn, rheumatism, kidney problems, and some skin conditions. The early settlers learned about this root's amazing medical properties in the 1800's and Oregon grape tonics were a popular market commodity. Herbalists recommended soaking the roots in warm beer to relieve hemorrhaging.
The active ingredient that makes Oregon grape such an effective remedy is well known to us today. It is an alkaloid called berberine (which powerful healing constituent is found also in goldenseal). Berberine stimulates bile secretions and modern herbalists and homeopaths believe it promotes good liver function and purifies the blood. Most herbal manuals recommend steeping an ounce of dried root in a cup of tolling water, with a dosage of 3 tbsp. daily, although they warn that persons with over active livers should stay away from this root.

Other Uses:
Creeping mahonia was used by the Navajo to make a lavender dye from the berries and a yellow dye from the roots and underbark. Yellow stem wood was used by Native Americans to produce a bitter tonic. Plants form suckers freely, making a good dense ground cover, though they can be slow to become established.