Thaw fish, if frozen. Rinse fish; pat dry with paper towels. For blueberry-pepper jam: In a medium bowl, use a potato masher or fork to mash 3/4 cup of the blueberries. Stir in the remaining 3/4 cup blueberries, the 1 teaspoon sage, and the 1/2 teaspoon pepper. Cover and chill until ready to serve.
In a small bowl, combine crushed croutons, the 1/4 cup sage, the 1 teaspoon orange peel, and the 1/4 teaspoon pepper. Add orange juice and the 1 tablespoon olive oil, stirring until lightly moistened; set aside.
Lightly grease the rack of a grill. For a charcoal grill, place fish, skin sides up if using fillets, on the rack of an uncovered grill directly over medium coals. Grill for 5 minutes. Turn fish; top fish evenly with crouton mixture, gently pressing onto fish. Grill for 7 to 10 minutes more or until fish flakes easily when tested with a fork. (For a gas grill, preheat grill. Reduce heat to medium. Place fish on greased grill rack over heat. Cover and grill as above.)
To serve, place fish on a serving platter. Serve with blueberry-pepper jam. If desired, drizzle fish with additional olive oil. If desired, garnish with sage leaves.