To prepare the peppers, slice the tops off and remove any veins or seeds inside. In a medium-sized saucepan over medium-high heat add the olive oil and onion. Cook until almost tender. Add in the ground beef and cook and crumble until no longer pink.
Add in the diced tomatoes, tomato sauce, rice, Italian seasoning, garlic powder, and salt and pepper.
Lay a sheet of Reynolds Wrap® Non-Stick Foil on the bottom of each pepper.
Stuff the peppers with the mixture and top with cheese. Fold up each side of the aluminum foil and wrap the pepper.
Preheat the grill to 400° F. Place the wrapped peppers on the grill and cook until the peppers start to soften and cheese is melted, about 25–30 minutes.