Mix in the flour, powder, soda, salt, and cinnamon until combined. Stir in oatmeal and chocolate chips until combined, the batter will be very stiff.
Bake for 9 minutes, they will not look completely done but will be slightly brown around the edges. Move to a wire rack and cool completely.
For the chocolate chips in this recipe you can use a classic semi-sweet, but my favorite is to use a combo of semi-sweet, milk, dark, and/or white.
Old Fashioned Chocolate Chip Oatmeal Cookies from Sam's Dish http://samsdish.com/old-fashioned-chocolate-chip-oatmeal-cookies/