Tasty "poppers" are made various ways by many good chefs. Here is a slightly different approach. I use a mild pepper which is about the length of a hotdog bun. You can serve it in a bun or by itself. Either way, they are delicious, and are appreciated by those who do not care for the heat of jalapeño.
Using a meat tenderizer, pound the flat iron steak to flatten it out.
Cut steak into strips 3/8" wide and 5" long.
Cut peppers in half lengthwise and remove seeds and veins.
Mix cream cheese and cheddar cheese.
Fill peppers with cheese mixture.
Lay a strip of steak on top of the cheese mixture.
Wrap with a strip of bacon.
From here you can go two ways.
1) Put it in a conventional oven at 350 degrees until the bacon is crisp.
2) Put it on a smoker grill at 200 degrees for a few hours, until bacon is crisp.
Optional: when the bacon is crisp and appears to be done, spread BBQ sauce on each of the poppers and bake or grill for another 15 minutes or so.