
Spoon the sausage mixture evenly into each raw pepper half, gently pressing it down so it fills the peppers all the way to the top.
Pour the remaining 1 cup marinara sauce around the peppers and lightly over the tops, letting it run down into the bottom of the slow cooker. Cover with the lid.

Cook on LOW for 4 to 6 hours or on HIGH for 2 1/2 to 3 1/2 hours, until the peppers are tender and the sausage filling is cooked through and no longer pink in the center.
About 15 minutes before serving, sprinkle the remaining 1/2 cup shredded mozzarella evenly over the tops of the peppers. Cover again just until the cheese is melted.

Carefully lift the stuffed peppers out with a large spoon or spatula, spoon some of the sauce from the bottom of the slow cooker over the top, and serve hot.
Variations & Tips
If your family loves spice, use hot Italian sausage or add a pinch of red pepper flakes to the filling. For a lighter version, swap in turkey or chicken sausage and use part-skim mozzarella. You can also change up the grain: leftover quinoa, farro, or even cauliflower rice will work in place of the cooked rice—just keep the total amount the same.

To sneak in a few extra veggies without adding more ingredients, choose a chunky marinara that already has onions and peppers in it. If you’re cooking for two, make the full batch, then pack the extra peppers into individual containers; they reheat really well in the microwave for quick lunches. To keep clean-up easy on extra-busy nights, line the slow cooker with a slow-cooker liner or lightly spray it with cooking spray before adding the raw halved peppers.