Mix karo syrup and sugar in a medium-large sauce pan. Bring to a boil over high heat, stirring constantly. Remove from heat and add peanut butter and vanilla. Mix well. Measure cereal into large bowl. Pour peanut butter mixture over cereal. Drop by spoonfuls on to wax or parchment paper.
The original recipe from Louise Barrett (Jamisons' next door neighbor) and Elaina Wendelboe (one of mom's Mia Maid advisors) calls for chunky peanut butter, but we've always used creamy.