Provençal Short Ribs with Olives and Herbs

Heat oven to 350 °F with rack in lower third. Stir together flour with 1 1/2 teaspoons salt and 1/2 teaspoon pepper in a bowl. Pat ribs dry and lightly dredge in flour mixture, knocking off excess. Heat 2 tablespoons oil in a wide 6- to 8-quart heavy pot over medium-high heat until it shimmers. Brown ribs in 3 batches, about 8 minutes per batch. Transfer as browned to a platter. Discard fat from pot. Cook onions, carrots, and celery in remaining 2 tablespoons oil with 1/2 teaspoon salt over medium heat, stirring occasionally, until just softened and beginning to brown, 8 to 10 minutes. Add garlic and herbs and cook, stirring frequently, until garlic is softened and fragrant, 2 minutes. Add wine and boil until reduced by half, about 8 minutes, then stir in broth, tomatoes with juice, and vinegar and bring to a simmer. Return ribs to pot. Cover with the lid, then place in oven, and braise until ribs are fork-tender, 3 to 3 1/4 hours. Transfer ribs with a slotted spoon to a bowl. Let cooking liquid stand briefly, then skim fat from top. Stir in olives. Adjust seasoning to taste, if necessary. Return meat to pot. Grate zest from orange over top just before serving.