1.In a large mixing bowl, combine oats, flour, sugar, salt, baking powder and cinnamon. Mix with a whisk to break up any clumps.
2.Toss in butter chunks. Using your cool fingers or a pastry cutter, combine until you have a crumbly mixture.
3.Press half into the prepared pan. Press down lightly and make sure you go all the way to the corners.
4.Spread jam with a rubber spatula or an offset spatula.
5.Sprinkle the rest of the crumble over the top of the jam. Gently pat down.
6.Bake for about 30 to 40 minutes until the top turns light brown.
7.Let cool on wire rack about 15 to 20 minutes for eating them warm. Cut into squares.