COOK peppers and garlic in margarine on medium heat until tender-crisp, about 2 minutes. Remove from skillet.
BLEND chicken broth and mustard in same skillet. Simmer uncovered, stirring occasionally for 3 to 4 minutes or until slightly thickened. Stir in peppers until throughly heated.
SPOON over hot fettuccine; toss to coat.
Storage Know-How: Store bell peppers in plastic bag in refrigerator for up to 1 week.