View photos of the edible and medicinal plant Quercus gambelii (Gambel oak), profiled in Medicinal Plants of the Western Mountain States.

A passage from  Medicinal Plants of the Western Mountain States:

As a short–term internal tea, the plant is appropriate for a number of conditions. Bleeding ulcers, be them esophageal, stomach, or intestinal centered are soothed and astringed. Diarrhea is symptomatically addressed with a strong brew of Oak tea. Best taken after most of the offending contents have been voided, it lessens hypersecretion which often leads to exhaustive emptying. If intestinal cramping is present, the addition of Yellow pond lily or Western peony will be found useful. For serious spastic activity, Silk tassel tincture (or Henbane…be careful) should be employed.