Combine cabbage, carrot, onion, grapes, jalapeño, oregano, vinegar, sugar, and salt in a large bowl.
Cover and refrigerate at least 1 hour or up to 24 hours ahead.

Combine the flour, chili powder, salt, and pepper in a shallow bowl or pie plate. Dredge the fish in the flour mixture. Heat the olive oil in a large non-stick skillet over medium-high heat. Add the fish and cook 4 minutes; turn and cook another 2 minutes. Remove to a bowl and flake the fish. To serve, divide the fish among the tortillas and top with curtido. Serve with lime wedges.