Thaw fish, if frozen. Rinse fish; pat dry with paper towels. If necessary, cut fish into 4 serving-size pieces. For marinade, in a blender container combine chipotle peppers, adobo sauce, sweet pepper, lime juice, oregano, and garlic. Cover and blend until pureed. Transfer half of the marinade to a shallow dish; set aside remaining marinade.
Add fish steaks to dish, spooning some of the marinade over fish. Cover and marinate at room temperature for 30 minutes.