Preheat the oven to 350 degrees F. Grease a 9x13 inch baking dish with butter or line with parchment paper. In a large mixing bowl or the bowl of a stand mixer, mix the oatmeal, flour, brown sugar, granulated sugar, baking soda, salt, canola oil, eggs and vanilla. Beat until the dough is moist and all the ingredients are combined. The dough will be crumbly. Mix in the chocolate chips and 1/4 cup candy pieces.Press the dough into the prepared baking dish and scatter the remaining 1/4 cup candy over top. Transfer to the oven and bake 18-20 minutes or until the edges are set and the bars are golden. Let cool and then cut into bars.