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1
Heat the oven to 350 degrees F and arrange a rack in the middle.
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2
Coat a 9-by-9-inch metal baking pan with butter, then flour, tapping out any excess flour; set aside.
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3
Place the measured flour, oats, sugars, salt, and baking soda in a large bowl and whisk to combine.
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4
Add the peanut butter and, using your fingers, squeeze the oat mixture and peanut butter together until evenly combined.
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5
Scatter the measured butter pieces over the mixture and, using your fingers, squeeze the peanut butteroat mixture and butter together until evenly combined and no large pieces of butter remain.
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6
Place two-thirds of the mixture into the prepared pan and, using a measuring cup dipped in flour, press it firmly and evenly into the bottom; set the remaining mixture aside.
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7
Bake until the edges start to brown, about 15 minutes.
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8
Remove the pan from the oven to a wire rack.
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9
Dollop the jam over the crust and spread into an even layer, taking care not to disturb the crust.
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10
Crumble the reserved oat mixture into pieces about the size of almonds and evenly sprinkle it over the jam.
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11
Return the pan to the oven and bake until the jam is bubbling and the topping is golden brown, about 20 to 25 minutes more.
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12
Remove the pan to the wire rack and let it cool completely, about 1 1/2 hours.
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13
Cut into 18 (3-by-1-1/2-inch) bars.
