This is okay as a basic starting point, but is missing some seasoning. Add 2-3 cloves minced garlic, minced fresh parsley and marjoram to the stuffing, Plain meat and rice is rather bland. Also, especially if you are using brown rice, cook the rice until almost done. When you are mixing the filling, make sure to add a beaten large egg to the mix. Bell peppers can be bitter, try using Hungarian wax or some other pepper with a little heat and sweetness to its flesh
We like stuffed peppers around here, but these were very bland and tasteless. I can't put my finger on what was missing, but definitely won't be making again.