In a medium bowl, combine first 5 ingredients (through crushed red pepper). Rinse scallops under cold water; pat dry. Add scallops to marinade; toss well to coat. Let stand 10-30 minutes, stirring once.
Bring broth to a boil in a medium saucepan over high heat. Reduce heat; stir in couscous, peas, carrots, and salt; cover and turn off heat. Let stand 5 minutes.
Meanwhile, prepare grill, and grill scallops over medium-hot coals 3 minutes per side or until golden brown and opaque in center. Arrange couscous mixture on 4 plates. Arrange 4 scallops over couscous. Bring marinade to a boil, stir, and cook 3 minutes or until thickened. Drizzle mixture over scallops and couscous; top with cilantro, if desired.