Saute the chopped onion in butter. Add ground beef and brown lightly. Drain off any excess fat. Add all of the remaining ingredients and simmer covered for 30 minutes. Cool mixture and freeze using the freezer bag method.
For those new to the freezer bag method...
When using the freezer bag method for freezing, you place your meal in a freezable bag, (like a Ziploc or FoodSaver bag) then remove as much air as you can, and seal. Then take a cake pan, or a pan that has sides, and lay the bags flat, stacking them on top of each other. The cake pan will freeze your meals in a nice flat shape giving you more freezer room and also ensure that any leaks stay within the pan. You then place the pan in the freezer. Once it has been flash frozen, (frozen just enough to hold it's shape) remove the items from the pan and store it however you like in your freezer. It is also a good idea to place your meal back in a pan in the fridge while thawing so you don't have leaks then either.
To Prepare After Freezing:
Remove from freezer and let thaw. Heat mixture slowly in a skillet or saucepan until warmed all the way through and ready to serve. (We like to eat it on fresh warmed whole wheat hamburger buns!)