Preheat the oven to 400 degrees and spray a large 9"x13" baking dish with cooking spray.
Wash and half each bell pepper through the stem removing the stem and seeds.
Rub each bell pepper half with the 1 tbsp of olive oil.
Prepare the rice according to the oven baked rice instructions.
Place the bell peppers and rice in the oven to cook.
Cut or shred your roasted beef and add it to a large bowl.
After the rice cooks, add it to the large bowl with the roasted beef along with ½ tsp onion powder, ½ tsp garlic powder, 1 tsp black pepper and ½ tsp of sea salt. Mix until thoroughly combined.
Add 1/2 the cheese to the rice mixture.
After the bell peppers have roasted for about 30 minutes, remove them from the oven.
Divide the rice mixture among the 8 bell pepper halves. Top each half with the remaining cheese.
Reduce the oven temperature to 350 and cook the bell peppers for 20 additional minutes.
Serve warm.