Stir together the flour, rosemary, mustard, salt, garlic powder, and pepper in a bowl. Dredge the pork chops in the seasoned flour, shake off excess, and set aside. Heat the vegetable oil in a large skillet over medium-high heat. Add the pork chops and cook until golden brown on both sides, about 4 minutes per side.
Place the onion, mushrooms, and garlic into a slow cooker. Add the seared pork chops, then pour in the cream of mushroom soup and Marsala wine. Cover, and cook on Low until the chops are tender, 6 to 8 hours.
