Brush 1 1/2 teaspoons olive oil evenly over tuna steaks. Sprinkle 1 teaspoon pepper over both sides of tuna, pressing pepper into tuna.
Coat grill rack with cooking spray; place on grill over medium-hot coals (350° to 400°). Place tuna on rack; grill, covered, 4 minutes on each side or until fish flakes easily when tested with a fork.
Flake tuna in a medium bowl. Drain red peppers, reserving liquid. Chop enough peppers to measure 3/4 cup. Reserve remaining peppers and liquid for another use. Add chopped peppers, remaining 1 tablespoon olive oil, tarragon, and lemon juice to tuna, stirring lightly. Finely chop 1 clove garlic; add to tuna mixture. Set aside.
Lightly coat both sides of bread slices with cooking spray. Cut remaining 1 clove garlic in half; rub bread slices with cut sides of garlic. Arrange bread slices in a single layer on a baking sheet. Bake at 350° for 10 minutes or until lightly browned, turning once. Spoon tuna mixture evenly over bread slices.