2. Mix together sugar, margarine and corn syrup in 2-quart saucepan; cover and cook over medium heat, stirring constantly, until mixture boils.

3. Continue boiling, stirring occasionally, until temperature on candy thermometer reaches 290 F., or until small amount of syrup dropped into very cold water separates into threads which are hard but not brittle.

4. Remove from heat and stir in vanilla; pour over popped corn mixture, stirring to coat well.

5. Spread out to cool. Break into pieces and store in tightly covered container.