I bought a whole bag of mini sweet peppers at the local big box store. These were easy, fairly quick, and a hit when I made them up. You can spice these up, since they really aren't very spicy despite using a spicier sausage.
Prep the ingredients by:
-- remove the casings from the sausage
-- chop the onion into a small dice.
-- choose only larger peppers from the bag. Cut the tops completely off each pepper. Cut the bottoms off, too, so that you can see all the way through the pepper. Remove the veins and seeds from inside the peppers using a veggie peeler or small knife. Shake the seeds and veins out of the peppers.
-- dice the peppers' bottom ends.
In a skillet over medium high heat add the oil. When it comes to temperature, add the onions and peppers. Sauté the veggies until they soften. Remove from the heat and let them cool slightly.
Mix all ingredients together in a bowl. Add more cheese if you want your peppers cheesier.
Stuff each pepper with the meat mixture. Place each one in a "bowl" of a mini muffin pan.
Bake in a 375 degree oven for 30 minutes or until the peppers look soft and roasted. The grease from the sausage will collect in the mini muffin "bowl", so remove the peppers to a paper towel to cool.