Step 1: Melt Butter - In a medium bowl, melt 1 ¼ cups of unsalted butter in the microwave for 30-45 seconds.

Step 2: Combine Base Ingredients - Mix melted butter, 1 ½ cups of quick oats, 2 ¼ cups of all-purpose flour, and 1 ½ cups of brown sugar until crumbly.

Step 3: Press Crust into Pan - Grease a 9x13 inch baking pan and press two-thirds of the mixture into the bottom.

Step 4: Bake Crust - Preheat oven to 325°F and bake the crust for 10 minutes until lightly golden.

Step 5: Prepare Caramel Filling - In a saucepan, melt ¼ cup of butter with 1 cup of brown sugar until smooth.

Step 6: Mix Remaining Ingredients - Add ¼ cup of milk, 2 teaspoons of vanilla extract, and 2 tablespoons of flour, stirring well.

Step 7: Simmer Caramel - Bring the mixture to a gentle boil, stirring constantly for about 3 minutes.

Step 8: Assemble Bars - Pour the warm caramel filling over the crust and spread evenly.

Step 9: Top with Crust Crumbs - Sprinkle reserved crust crumbs over the caramel layer.

Step 10: Bake Again - Lower oven to 300°F and bake for 20 minutes until set and lightly browned.

Step 11: Cut and Serve - Let cool, then slice into squares or rectangles to serve.