1 1/2cupsshredded cheddar cheese(alternatively you can use mozzarella, Monterey jack, or other shredded cheese blend that melts easily)
Prepare the Grill for indirect cooking, or set the grill to 375 degrees F.
Prepare the peppers: cut the tops off the peppers, remove seeds and membranes (discard the seeds and membranes).
Make the rice: Prepare the rice according to the rice packaging directions.
Cook the Filling: Heat a large cast iron pan to medium heat, add one tablespoon of olive oil and the onions and cook 5 minutes to soften. Add the ground beef and cook, breaking up the beef with a spatula, until cooked through (about 6-8 minutes). Add the garlic and cook 1 minute.
Mix in remaining filling ingredients: add the remaining filling ingredients to the cast iron pan, including the cooked rice, tomatoes, Worcestershire, green chilies, salt, pepper, and thyme. Remove from heat and add half of the cheese. Stir to incorporate. Taste and season as needed.
Stuff the Peppers: Stuff about 1/4 cup of the filling into each pepper. The exact amount may vary based on the exact size of your peppers. Add equal amounts into each pepper. Top the peppers with remaining cheese.
Grill Peppers: place peppers, cut side up, over indirect heat and cook 30-40 minutes, until the peppers are tender and look slightly roasted and the cheese has melted. (If your peppers don't feel sturdy standing up on their own pack them all upright in a cast iron dish to help support them standing upright.)
What to do with the pepper tops: after discarding the seeds and membranes you can chop up the pepper tops and add them to the mix at the same time as the ground beef.