Heat the oven to 350°F (175°C). Line an 8-inch square baking pan with parchment paper, leaving enough overhang on two sides to lift out the cooled bars.

Stir the flour, rolled oats, brown sugar, baking powder, and salt together in a large bowl. Add the melted butter and vanilla, then mix until moist, coarse crumbs form.

Press approximately two-thirds of the crumb mixture firmly into the prepared pan. Bake the base for 10–12 minutes, until lightly set but not deeply browned.

While the crust bakes, place the unwrapped caramels and evaporated milk in a saucepan over low heat. Stir frequently until smooth, keeping the mixture below a boil.

Spread the strawberry preserves evenly over the warm crust. Pour the melted caramel over the preserves, distributing it carefully from edge to edge.

Scatter the remaining crumble mixture over the caramel layer without compacting it. Bake for another 25–30 minutes, until the topping is lightly browned and the caramel bubbles at the edges.

Cool the bars completely in the pan for at least 1 hour. For cleaner slices, refrigerate them for 30–60 minutes before lifting them out and cutting into 16 bars.