My favorite oatmeal cookie recipe is from Better Homes & Gardens.

3/4 cup butter, softened
1 cup packed brown sugar
1/2 cup granulated sugar
1 teaspoon baking powder
1/4 teaspoon baking soda
1/2 teaspoon ground cinnamon
1/4 teaspoon ground cloves
2 eggs
1 teaspoon vanilla
1 3/4 cups (7 oz) all-purpose flour
2 cups rolled oats
1 cup raisins, dried cranberries, or chocolate chips (optional)

Preheat oven to 375°F.

In a large mixing bowl beat butter with an electric mixer on medium to high speed for 30 seconds. Add brown sugar, granulated sugar, baking powder, baking soda, cinnamon, and cloves. Beat until combined, scraping sides of bowl occasionally. Beat in eggs and vanilla until combined. Beat in flour. Stir in oats and raisins.

Drop dough by rounded teaspoons 2 inches apart onto an ungreased cookie sheet. I use a scoop so that they're all the same size (#40 scoop for regular cookies, #60 for mini ones). I also press down the dough slightly before baking. Bake for 8-10 minutes or until edges are golden. Cool on cookie sheet for 1 minute then transfer to wire rack to cool completely.