Preheat the oven to 350 degrees and prepare a 9 x 13 baking pan with nonstick spray.

In a large skillet Brown the sausage with the onion. Drain the grease and return to the pan.

Add the rice and water to the skillet and bring to a boil. Reduce to a simmer and cook covered for 15 minutes.

Stir in the chopped zucchini and tomato sauce to rice mixture. Cover and cook another 5 minutes or until rice is tender.

Meanwhile while the filling is cooking, cut the tops off the peppers. Scoop out all the seeds and membranes. Cut off ¼ inch of the bottoms of the peppers, if needed, to level off and allow to sit upright in the pan. 

Once the rice is tender, remove from the heat and stir in 1/2 the cheese. Season the filling to taste with salt and pepper.

Stuff the peppers with the rice filling and place in prepared 9x13 inch pan. Cover with foil and bake for 40 minutes.

Remove the foil, top with remaining cheese and heat again just until cheese is melted.