In a skillet over medium heat, cook the ground beef until browned. Drain excess fat if needed.
Add the diced onion, green bell pepper, red bell pepper, and minced garlic to the skillet. Sauté until the vegetables are tender, about 5 minutes.
Transfer the beef and vegetable mixture to a 6-quart slow cooker.
Add the Italian seasoning, salt, pepper, tomato sauce, diced tomatoes, and beef broth. Stir everything together until well combined.
Cover and cook on high for 3.5 hours.
About 1 hour before serving, cook the macaroni according to the package directions and drain.
30 minutes before serving, stir the cooked pasta and frozen peas into the crockpot. Cover and let sit for the remaining cooking time so the flavors combine.
Garnish with fresh herbs or a sprinkle of shredded cheese if desired, and serve hot.
Enjoy!