Heat oven to 350 F.

Line 8x8 baking dish with foil and spray with cooking spray.

In a bowl with electric mixer, beat together butter and brown sugar until well combined, about 1 minute.

Add in flour, oats, baking powder, salt and cinnamon; mix until crumb mixture forms.

Press half of the mixture into the bottom of the prepared pan.

In a separate bowl, whisk together the sweetened condensed milk, orange zest and orange juice.

Pour orange mixture on top of crust.

Sprinkle with remaining crumb mixture.

Bake for 30-32 minutes, until golden on the edges and set in the middle. It will still seem kind of jiggly but it will set up as it cools.

Cool completely. Remove bars from the pan with the foil and peel foil from edges. Cut into bars.