Warm peanut butter, vanilla and honey in a sauce pan over medium heat. Stirring constantly. Once warm and smooth, add milk and stir to combine. Alternatively, heat the peanut butter, vanilla and honey in a microwave in 30-second increments, stirring between until smooth, adding vanilla once warmed.
In a large bowl, combine oats and warm peanut butter mixture. Stir well. Portion into (2) ½ cup servings and top each portion with ½ cup frozen mixed berries on each portion. Cover and refrigerate overnight or for at least 2 hours. Serve cold.
(Optional variation: for chocolate banana peanut butter oats, add 1 tablespoon cocoa powder and substitute 1 cup sliced banana for the mixed berries)