Preheat oven to 375ºF. Prepare a 9x13 baking dish by lining it with parchment paper.
Using a stand mixer or by hand, mix the butter, brown sugar, and eggs.
Add in the milk, vanilla, flour, baking soda, salt, and oats, and mix well.
Stir in the chocolate chips, Rolos, and pecans.
Spread the dough in the prepared baking dish, and bake for approximately 20-25 minutes. The edges should be set and golden brown, and the tops of the bars should look mostly "dry."
Allow to cool for at least 10 minutes before cutting.