Cook fettuccine to desired doneness as directed on package. Drain. Return to saucepan. Add margarine; toss to coat. Cover to keep warm.
Meanwhile, heat oil in large skillet over medium-high heat until hot. Add chicken; cook 4 to 5 minutes or until no longer pink, stirring occasionally. Add onion and mushrooms; cook and stir 2 to 3 minutes or until onion is tender.
Sprinkle flour over chicken mixture; cook and stir 1 minute. Stir in tomatoes and green chiles. Bring to a boil. Reduce heat to low; cover and simmer 5 to 10 minutes or until sauce is slightly thickened, stirring occasionally.
To serve, arrange cooked fettuccine on serving platter. Spoon chicken mixture over fettuccine. Sprinkle with cheese.