In a large skillet cook the sweet pepper and onion in hot oil just until tender. Stir in the mangoes, brown sugar, vinegar, crushed red pepper, and salt. Bring to boiling; reduce heat. Simmer, uncovered, about 10 minutes or until mangoes are tender. Cool mixture slightly. Transfer mixture to a blender container or food processor bowl. Cover and blend or process until nearly smooth. Stir in the green onion.
To use, brush chicken, shrimp, fish, or pork with some of the sauce during the last 10 minutes of grilling. If desired, reheat and pass additional sauce. Makes about 2-1/2 cups.