In 3-quart saucepan, melt butter over medium heat. Add green onions; stirring frequently, cook 5 minutes. Add flour. Stirring constantly, cook 1 minute. Gradually stir in half-and-half until smooth.

Stirring constantly, bring to a boil. Stir in oyster liquor and Tabasco pepper sauce. Continue stirring constantly, cook until soup thickens. Add oysters and parsley. Stirring frequently, cook over low heat 5 to 10 minutes longer (do not boil).