Preheat oven to 350°F (176°C). Lightly grease a 9x13-inch pan.
In a small saucepan, combine 1/2 cup long grain white rice with 1 cup water. Bring to a boil over high heat. Once boiling, reduce the heat to medium-low, cover, and steam until all water has been absorbed, about 15 minutes.
Meanwhile, trim the tops off 6 medium bell peppers and remove seeds and membrane from inside. Place the bell peppers into the prepared pan. Bake for 10-15 minutes.
While the bell peppers are cooking, cook 1 pound ground beef and 1 medium white onion in a 12-inch skillet over medium high heat until the beef is browned and the onions start to soften, about 5 minutes. Drain any excess fat or liquids. Add 3 teaspoons minced garlic and cook 1 minute more.
Remove from heat and stir in 1 (15 ounce can) diced tomatoes (drained), the cooked rice, 1 cup frozen corn, 1 tablespoon Worcestershire sauce, 1 1/2 teaspoon salt, 1/2 teaspoon black pepper, and 1 cup shredded pepper jack cheese.
Remove bell peppers from the oven and spoon the ground beef mixture into bell peppers until full. Sprinkle remaining cheese over the top.
Bake, uncovered, in the preheated oven for 30 minutes until cheese is bubbling and browned.