Heat oven to 350°F. Line a 9 x 13-in. baking pan with nonstick foil, leaving a 3-in. overhang on two sides. In a food processor, pulse ½ cup flour, the brown sugar and ¼ cup (½ stick) butter until the mixture forms large crumbs. Transfer to a medium bowl and stir in ½ cup oats. Refrigerate until ready to use. Spread the jam evenly over the batter. Crumble the chilled crumb mixture into small clumps over the jam. Bake until the jam is bubbly and a wooden pick inserted in the center comes out clean, 22 to 25 minutes. Let the bar cool in the pan for 30 minutes. Using the overhangs, transfer the bar to a wire rack to cool completely. Cut into pieces.