Heat half the oil in a large casserole dish over medium-high heat. Season brisket and sear for 2 to 3 minutes each side or until browned. Set aside on a plate.
Heat remaining oil over medium heat and cook half the garlic, onion, carrot, celery, capsicum for 4 to 5 minutes or until softened. Add tomatoes, stock, oregano, rosemary and vinegar. Return beef to dish, bring to the boil, cover and transfer to the oven. Season and cook for 2 to 2 1/4 hours, or until tender, basting brisket occasionally with sauce. Rest beef loosely covered with foil for 10 minutes before slicing. Stir olives through sauce, reducing on stovetop if desired.
Meanwhile, place remaining garlic, parsley, lemon zest and juice in a small bowl. Season and stir to combine.
Thinly slice brisket. Serve with sauce, polenta, gremolata and green beans.
This recipe also is perfect for a rolled beef brisket.
Swap polenta for creamy mash or sweet potato mash.
Add some fresh chilli to the sauce for a spicier dish.