- Preheat your oven to 350°F.
- In a large bowl, mix together the ground beef, spinach, zucchini, onion, cooked brown rice, egg, oregano, salt, and pepper until well combined.
- Slice the bell peppers in half lengthwise and arrange them cut side up in a baking dish. Spoon the meat mixture into each pepper, filling them about halfway. Pour the diced tomatoes evenly over the top and sprinkle with crumbled feta cheese.
- Cover the dish with foil and bake for 30 minutes. Then remove the foil and continue baking for another 25 minutes, or until the meat is fully cooked and the peppers are tender.
- Enjoy!