In a nonstick skillet, cook the bacon over moderate heat, stirring occasionally, until crisp, about 8 minutes. Using a slotted spoon, transfer the bacon to paper towels. Pour off all but 4 tablespoons of the fat.

Add the endives to the skillet. Cook over moderately high heat, stirring occasionally, until golden brown and softened, 6 minutes. Stir in the bacon; season with salt and pepper. Transfer the endives to a bowl and keep warm. Wipe out the skillet.

Heat the vegetable oil in each of 2 large nonstick skillets. Season the fish with salt and pepper and add the fillets to the skillets, skin side down. Cook over moderately high heat until the skin is browned and crisp, about 4 minutes. Turn and cook until the flesh is just white throughout, 2 minutes longer. Add the grapes to the skillets and cook, stirring, until hot, about 1 minute. Transfer the fish and grapes to the plates on top of the endives and serve.