Corn Chowder

6 medium ears of corn or 2 (10 oz) pkgs frozen corn 2 tbsp margarine
2 cups cooked, diced boiled potatoes 2 tbsp all-purpose flour
4 cups milk 1 tsp salt
1 lrg onion, chopped 1/4 tsp pepper

Melt margarine in top of double boiler, add onion. Cook slowly until soft but not golden. Mix in flour and then add milk slowly. Stir until slightly thickened; add remaining ingredients. Place pan over boiling water for 20 minutes, stirring occassionally.