Heat oven to 350°F. Grease 13x9x2-inch baking pan (...or whatever you own. I could only find my square pan. The smaller the pan, the longer you may have to bake the bars since they will be much thicker).
Beat butter and brown sugar in large bowl until well blended. Add eggs and vanilla. Beat well. Stir together flour, baking soda, cinnamon, and salt; gradually add to butter mixture, beating until well blended. Set aside 1/4 cup toffee bits.
Stir remaining toffee bits and oats into batter.
Spread batter into prepared pan. Sprinkle reserved toffee bits over surface. Bake 25 minutes or until wooden pick inserted in center comes clean.
Cool completely in pan on wire rack. Cut into bars.