Whisk together flour, old-fashioned oats, baking powder, baking soda and salt in a mixing bowl.
In another bowl mix butter, brown sugar, white sugar, eggs and vanilla extract using a mixer.
Combine wet and dry mixtures and continue mixing until all ingredients are wet. Fold in chocolate chips and nuts with spoon. I kept out a few chocolate chips and a few nuts to sprinkle on top of batter before cooking in pan.
Spray a 9 x 13 baking pan and bake in preheated 350 degree oven for 25 to 30 minutes or until the center test done.
Let cool before cutting in squares. Makes about 15 to 20 bars depending on size you cut them.
Notes
Can make these using all kinds of chips like peanut butter, butterscotch, etc. Could add raisins and can omit nuts.