Step 1

Preheat the oven to 350 and spray a baking dish with cooking spray.

Step 2

Prepare the peppers and the filling. Use a knife to cut each bell pepper stem in half. Remove the ribs and the seeds. Season the inside of each pepper with salt and pepper. Place the peppers into the greased baking dish in one layer. Set aside.

Step 3

Cook the filling. Heat the olive oil in a large frying pan over medium heat. Add the ground beef, season with salt and pepper, and cook, stirring occasionally, until browned. Add the onions, zucchini, garlic, and oregano, and cook until softened. Stir in the crushed tomatoes. Taste and season with salt and pepper as needed. Remove from heat.

Step 4

Stuff the peppers. Evenly divide the mixture among the peppers. Carefully pour 1/2 cup of water between the peppers into the baking dish. Cover with foil.

Step 5

Bake until the peppers are tender and the filling is heated through -- about 45 minutes. Remove the foil and sprinkle the peppers with shredded cheese. Return to the oven until the cheese is melted -- about 5 more minutes. Remove from the oven and garnish with scallions and herbs, if desired, before serving.