Preheat your oven to 375° F.
Lightly grease or oil your cookie or baking sheet.
Using a mixing bowl, blend your cookie mix, oats, baking soda, salt, cinnamon, and set aside.
Vegan Egg Substitute: follow the instructions on your egg-replacer package. Or, if using flaxseed, measure out 1 tablespoon flaxseed and 3 tablespoons water. Grind the flax seeds into a fine powder. If you have pre-ground flaxseed, 3/4 tablespoon should work. Combine the flaxseed and water and then whisk until the mixture becomes gelatinous. Substitute for the eggs in the next step.
Put your butter/margarine or shortening, brown sugar, egg or egg substitute, milk, and vanilla extract into a large mixing bowl. Beat on medium until well-blended.
Gradually mix your dry ingredients into the wet mixture until well-blended. By hand, stir in raisins or craisins, chocolate chips, or nuts if desired.
Drop rounded teaspoons of cookie dough 2 inches apart onto your ungreased cookie sheet. Cookies may be made larger by using a larger spoon such as a tablespoon but remember to leave more space between them to allow for expansion while they bake.
Put your cookie sheet in the oven and bake your cookies for 10-12 minutes, until lightly brown.
Remove your Chewy Oatmeal Cookies from the oven and let them rest for two minutes. Then, using your spatula, move the cookies from your baking sheet to a wire rack to finish cooling. You can definitely eat 'em warm!