Season the meat with salt and pepper, and dredge in flour. Shake off any excess
Heat butter in a large skillet over medium heat until melted.
Add meat and brown in the hot butter for about 5 minutes on each side, until browned on both sides.
Place beef to crock pot
Add the grape juice to the skillet and scrape any browned bits from the bottom. Add the tomatoes, celery, onion, carrots, thyme and garlic to the skillet.
Pour the contents of the skillet into the crock pot. Cover and cook on low for 6-8 hours.
Transfer the meat to a platter and cover to keep warm.
Pour the sauce from the crock pot into a skillet and simmer over medium heat until reduced to about 2 cups. Season to taste with salt and pepper
In a small bowl, combine the parsley, lemon zest and garlic to make a gremolata garnish.
Serve the Osso Bucco topped with sauce and gremolata