Preheat oven to 350 degrees F (175 degrees C). Grease a 9x13 inch baking pan.
In a large bowl, stir together the oats, flour, brown sugar, salt and baking soda. Cut in the butter to form a crumbly mixture. Reserve 1 1/2 cups of the crumbs, and pat the rest evenly into the bottom of the prepared pan. In a medium bowl, stir together the sweetened condensed milk and peanut butter. Spread evenly over the oatmeal layer. Sprinkle the chocolate chips over the peanut butter layer, then crumble the reserved crust over the top.
Bake for 30 to 35 minutes in the preheated oven, until golden brown. Cool completely before cutting into bars.