Preheat charcoal or gas grill for direct cooking over medium heat (350°). Place large cast-iron skillet on grill rack; preheat 10 minutes.

Using kitchen shears, cut through top of lobster shells, down the center, just to tails. Split shells. Use thumbs and fingers to spread shells open. Gently loosen lobster meat from shells, leaving tail portions attached and lobster meat in shells; set aside.

Stir together butter, lemon zest, and juice, 2 tablespoons rosemary, 1 tablespoon chives, ¼ teaspoon crushed red pepper, garlic, salt, and black pepper in small bowl. Spoon butter mixture over lobster.

Transfer lobster tails to hot skillet. Grill 12 to 15 minutes or until lobster reaches 145°.

To serve, transfer lobster tails to serving plates. Garnish with additional rosemary, chives, and crushed red pepper; serve with lemon wedges, if desired.