We have always raised our birds in an open barn with access to the outdoors. However, what most people do not realize is that opening the barn door does not necessarily mean the chickens will go outside. These birds have been bred to gain weight fast, and all they want to do is sit at the feeder and eat. We move our feeders and water outside to encourage them to get out of the barn. But calling them free range still does not mean they have been eating grass and bugs. This is mostly because they sit on their (gr)ass and kill the vegetation, which seems to deter grasshoppers.
Part of my new plan is to grow leafy vegetables right in the chicken pasture. I will fence the young growth off until it is ready, and then let the chickens enjoy the salad bar! I have a few other ideas to try out as well, all aimed towards raising happy, and therefore delicious chickens. Another 20 years or so and I might have it figured out.