You can use the cheapest cuts of meat in this recipe because the vinegar in the peppers breaks down the fibers in the meat. This recipe is from The Best Slow Cooker Cookbook Ever by Natalie Haughton. I sometimes stuff the beef, peppers and chopped fresh tomatoes into pita breads.
This is an easy meal to put on the table. I love to make this in the fall and winter. The chile powder from New Mexico makes a lot of difference, but you could make your own chile powder from chile pods, or buy it at the store.
NOTE: If you buy chili powder (like McCormick) from the store, it is a blend of ingredients. Omit the oregano if you use it.
This is a combinations of many recipes I have used to make fajitas. I like this one best. You may also use pork tenderloin, pounded to 1/2" thickness instead of the skirt steak. Lamb or chicken could also be used.