Melt the margarine in a small frying pan over low heat.
Add the garlic and cook for 1 minute.
Cut each slice of bread into 9 squares and add to the frying pan.
Cook on both sides until light golden brown, drain on paper towels.
Arrange the watercress and chicken pieces on a serving plate.
Pour over French dressing and toss gently.
Arrange croutons on top and serve immediately.