MELT 2 tablespoons butter in medium saucepan over medium heat. Add onion and garlic; cook, stirring occasionally, for 1 to 2 minutes or until onion is tender. Transfer onion mixture to blender. Add red peppers; cover. Blend until smooth.
MELT remaining 2 tablespoons butter in same saucepan. Stir in flour. Gradually stir in evaporated milk and broth. Cook, stirring constantly, until mixture comes to a boil. Stir in red pepper mixture, salt and pepper. Heat through.