Preheat oven to 350 degrees.
In a mixer, stir brown sugar and butter until creamy.
Add eggs and vanilla and mix again.
In a mixing bowl, stir together the oatmeal, flour, baking soda and salt.
With mixer on low slowly add oats mixture to egg-butter mixture.
Add peanut butter chips to mixer. Continue to mix until all is blended.
In a medium-sized saucepan over heat, stir together the sweetened condensed milk, chocolate chips, and 3 T. of butter. Add vanilla. Stir until melted and smooth. Remove from heat.
In a 9″ x 13″ pan, pour in 2/3’s of the oats mixture evenly across pan. and pat down.
Pour fudge sauce across oats mixture and spread evenly.
Spread remaining 1/3 oats mixture across top of fudge and spread evenly.
Bake at 350 degrees for 30 minutes.
Remove from heat and allow to cool.