Heat convection oven to 300°F . Heat honey, oil and corn syrup in heavy saucepan on medium heat until blended, stirring frequently. Remove from heat and stir in vanilla.
Combine oats, sugar, OREO Base Cake, OREO Small Pieces and salt in large bowl. Add honey mixture; stir gently until combined. Stir in cocoa powders. Spread mixture onto parchment paper-lined sheet pan.
Bake for 1 hour. Cool completely on pan. Toss with OREO Medium Pieces in large bowl. Store in airtight container at room temperature until ready to use.