In Loren Cordain's research he looked at what actual hunter-gatherers ate, those alive today and the archaeological records of those in the past and he found that very few cultures actually ate grains (oats, wheat, barley, rye, corn, rice) in any appreciable quantity. They were usually eaten under duress during times of famine. Also, he demonstrates that they are nutritionally poor for their calories compared to other foods, and that cultures that adopted grains as a major portion of their diet suffered shorter stature, greater infant mortality, tooth decay and shorter lives. I suppose if you've met all your nutritional requirements and simply need more calories, grains are a good way to go. In fact, were I planning to hike another one of the long trails, I would probably use grains as filler in my meals to help me get more calories. But on a day-to-day basis, I can't see any real reason to consume them regularly.
Female, 5'3", 49, Starting weight: 163lbs. Current weight: 135 (more or less).
Starting squat: 45lbs. Highest squat: 167.5 x 2. Current Deadlift: 190 x 3