Had to make a couple adaptions as only had minced beef not ground, used half an onion, used wholemeal rice and instead of mozzarella used grated cheddar. I put the cheddar on after the first 10 mins in the oven, and put the oven on for a further 10 minutes rather than 15 to get a nice golden brown top.
I also don't know what kind of whack ass size of bell peppers you have in America but the recipe would have made 10 however I used the left overs to create spaghetti bolonese.