Don't like the pepper part but I make a Low Carb Stuffed Mushroom that you could use to stuff the peppers with (much like the sausage one someone else posted) I also just put the stuffing into a dish and bake like regular stuffing instead of stuffing the mushroom caps.
1 pound fresh white mushrooms
2 tablespoons olive oil
6 ounces bulk Italian sausage (I use about 6 links and take off casing b4 browning)
1 teaspoon chopped garlic
1/2 teaspoon Italian seasoning
red pepper flakes (optional)
1 package Kraft Mediteranean Cheese Crumbles or 1/2 c mozzarella & 1/4 cup Parmesan cheese
Preheat oven to 400F. Remove stems from mushrooms; finely chop enough stems. Place mushroom caps in a bowl and toss with 1 tablespoon oil. Arrange caps cavity side up on a shallow baking pan and set aside.
Heat remaining oil in a medium skillet over high heat. Add sausage, red pepper, garlic, Italian seasoning and reserved chopped mushroom stems. Saute, breaking up sausage into smaller pieces, for about 5 minutes, until cooked through and nicely browned. Remove from heat; add cheese and stir just until cheese melts.
Stuff mushroom caps with sausage mixture and bake 10 to 15 minutes, until mushrooms are tender and cheese is slightly golden.