1Preheat oven to 350 degrees F (175 degrees C). Line a 9x13 inch baking pan with aluminum foil.
2In a medium bowl, cream together the butter, brown sugar and white sugar until smooth. Beat in the eggs one at a time, then stir in the vanilla. Combine the flour, baking soda, salt and cinnamon; gradually blend into the creamed mixture. Stir in the oats. Press the dough into the bottom of the prepared pan.
3Bake for 25 to 30 minutes in the preheated oven, until firm and lightly toasted at the edges. Melt chocolate chips in the microwave or in a metal bowl over a pan of simmering water, stirring frequently until smooth. Spread over bars. Cool completely before cutting into squares.