This summer we picked a ton of green beans all at once after returning from vacation. Many of them were over mature and tough. I found this recipe through an online forum.
Shelly Beans someone in New Mexico
Bacon
Onion
Green beans
Remove the beans from the pod (or I think this recipe actually softens up the pods pretty well - saves a ton of time and more nutritious!). Put cut-up bacon in hot pan, add chopped onion and saute. Then add beans and some water, cover with a lid. When the water has cooked down check to see if they're tender. If needed, add a little more water and cook a bit longer.