Cut the peels from the lemons, revealing the flesh. Cut the segments free from the membranes, then dice and place in a bowl. Squeeze any remaining juice from the membranes into the bowl. Set aside.
Heat a large nonstick pan over medium-high heat. Add 4 tablespoons butter and begin to cook, stirring, until the butter begins to brown. Add the brioche, then reduce the heat to medium-low and cook, continually tossing and swirling the brioche until evenly toasted, about 4 minutes. Remove the croutons to a plate and let cool. Wipe out the pan.
Sprinkle the fish with salt and pepper. Heat the same pan over medium-high heat. Add 4 tablespoons butter and the oil and begin to cook over the heat, stirring. Add the fish and cook, 2 to 3 minutes. Flip the fish and continue to cook, basting occasionally with the butter from the pan, another 2 to 3 minutes. Remove the fish to a plate. Wipe out the pan.
Turn the pan to medium heat and add the remaining 4 tablespoons butter. Let melt, then add the capers and cook for 1 to 2 minutes. Continue to cook until the butter browns, then add the wine, lemon juice and segments and parsley. Swirl together. Spoon the sauce over the fish and garnish with the croutons.