Preparation: Preheat your oven to 350 degrees F and prepare a 13-by-9-inch pan by lightly covering it with baking spray.
In a large bowl, whisk together the unbleached all-purpose flour, old fashion oatmeal, baking powder, and salt. Set aside.
In your stand mixer bowl, combine the unsalted butter, olive oil, light brown sugar, granulated sugar, and vanilla extract. Beat these ingredients together until creamy.
Add the eggs one at a time, ensuring each is fully incorporated before adding the next.
Gradually add the flour mixture to the wet ingredients while mixing on low speed until just combined.
Turn off the mixer and gently fold in the chocolate chips and toffee chips.
Scrape the dough into the prepared pan, smoothing the top with an offset spatula.
Bake in the preheated oven for about 22 to 25 minutes, or until the top is shiny and just starts to crack.
Remove from the oven and transfer to a wire rack to cool to room temperature.