Preheat the oven to 350°F.
In a small saucepan, whisk the butter, sugar, syrup and salt over medium-high heat until melted and smooth. Put the oats into a bowl - if you're using old-fashioned oats, you could pulse them a few times to grind them up a little if you like - and pour the caramel overtop. Stir to coat well, and spread into a parchment-lined 9x9-inch pan.
Bake for 20 minutes, until golden. Cut into squares or triangles while they're still warm. Makes 16.