Right now I've got more bell peppers than I know what to do with since I have red, yellow, and green pepper plants that are still bearing profusely. I've been making stuffed peppers off and on for about a month now. The great thing about stuffed peppers is you can use just about any leftovers and/or fresh ingredients for the stuffing.
Honestly, you can't go wrong with just about anything you stuff them with.
My basic stuffing consists of shredded or ground meat, a starch (rice or couscous or beans or torn bread or cracker crumbs), whatever fresh veggies I have on hand -- chopped, and fresh herbs and/or spices. I might also add seeds, nuts, and/or diced, crumbled, or shredded cheese. Cut and gut (take off the top and scoop out and discard the seeds and membrane) the peppers. I don't pre-cook or blanch. Set the stuffed peppers upright in a baking dish in a preheated 350 oven for about 45-60 min depending on the size of the peppers (I start checking them at the half-hour for doneness; they're done when the peppers are soft).
Last week I heated up a bit of leftover cooked ground beef and long grain and wild rice in a skillet with olive oil and a splash of Trader Joe's soyaki sauce, added some chopped pepper and sliced cremini mushrooms, heated until the veggies were cooked, then at the last minute added some fresh chopped Juliet grape tomatoes from the garden. Off heat I stirred in some fresh grated parmesan and chopped parsley from the garden. Stuffed and baked. Voila!