Preheat oven to 350°F. Grease an 8x8-inch pan and line with parchment paper. Set aside.
Place the oats in a food processor and pulse until coarsely ground. Set aside.
In a large bowl, whisk together the butter and brown sugar until slightly lightened in color. Add in the syrup, egg, and vanilla, and whisk until thoroughly combined.
Using a spatula, stir in the ground oats, flour, and salt until just combined. Fold in the walnuts. Pour batter into the prepared pan, spreading evenly.
Bake for 30-35 minutes, until the edges are golden and the center is set. Do not overbake.
Allow to cool in the pan, then use the parchment paper to lift the blondies out the pan. Cut into pieces and serve. Store in an airtight container for up to 4 days.