Preheat oven to 375 degrees. Line a 10x15* baking sheet with foil and grease lightly.
In a large bowl, mix together oatmeal, flour brown sugar, baking soda and salt. Add melted butter, mix until well combined and the mixture resembles coarse crumbs.
Reserve 1½ cups of the crumb mixture and press the remaining crumb mixture firmly into the bottom of the pan. Bake for 10 minutes.
In a small bowl, stir together sweetened condensed milk and peanut butter. Spread over the warm, partially baked crust within about ¼ inch of the edge.
Mix together reserved crumbs and candy pieces. Sprinkle over peanut butter layer and press down lightly.
Bake another 15-20 minutes until golden brown.
Cool completely before cutting into squares.
Notes
*You can make this in a 9x13 pan, just add a few minutes to each of the baking times.
Recipe by Crumbs and Chaos at http://www.crumbsandchaos.dreamhosters.com/2015/12/mm-peanut-butter-dream-bars/