Add about 1 tablespoon of olive oil to a skillet and sauté diced onions until translucent, about 3 minutes.
Add ground beef, breaking up and cooking until no longer pink.
While the beef is cooking, cut the tops off of the peppers, remove the seeds and membranes. Use a paring knife to cut out jack-o-lantern faces if desired.
Once beef is cooked, add the corn, rice, green chilies, black beans, and seasonings. Stir to combine and warm through.
Spoon some of the mixture into the prepared peppers, filling to the top.
Place peppers on a baking sheet lined with parchment or foil. Bake in the oven for ~15-20 minutes until peppers are soft.
Remove from oven and top with your choice of toppings.