Heat oil in a medium nonstick skillet over high heat just until hot. Sprinkle fish with salt and pepper. Sear fish 1 to 2 minutes on each side. Place rosemary sprigs in bottom of a lightly greased 11- x 7-inch baking dish. Place fish on top of rosemary in dish. Sprinkle fish with chopped rosemary, and top with lemon slices.
Bake at 450° for 10 minutes or just until fish is opaque.