Heat a large frying pan over high heat. Add the oil, then sear the beef, turning occasionally, until browned on all sides.
Combine the crushed tomatoes, onion and garlic in a slow cooker. Once the beef is seared, add to the slow cooker and season generously with salt and black pepper.
Cook on LOW for 8 hours or HIGH for 4-5 hours, or until the beef is tender and easily shredded with a fork.
Thirty minutes before the cooking time completes, preheat the oven to 220°C (200°C fan-forced). In a large baking tray lined with baking paper, place the zucchini, capsicum and cherry tomatoes. Drizzle the vegetables with olive oil, then toss with the garlic and a generous pinch of salt and black pepper. Roast for 15-20 minutes, or until tender.
Meanwhile, remove the beef from the braising liquid and shred with a fork. Return the meat to the liquid and stir to combine.
Serve the slow-cooked beef ragu with the roasted vegetables.
