Melt margarine in 4-quart saucepan or Dutch oven over medium heat.
Add onion; cook and stir until tender.
Reduce heat to low.
Stir in flour; cook and stir until mixture is smooth and bubbly.
Gradually stir in milk.
Add remaining ingredients.
Bring to a boil over medium heat, stirring frequently.
Reduce heat to low; simmer 10 to 15 minutes or until slightly thickened and vegetables are tender, stirring occasionally.