1 cup butter
3/4 cup brown sugar
1/2 cup sugar
2 medium eggs
1 tsp vanilla
1 1/2 cups flour
1 tsp baking powder
1/2 tsp baking soda
1 tsp salt
3 cups oatmeal
1 cup chocolate chips; or raisins

1. Preheat oven to 350F. Butter two large cookie sheets, or line them with parchment paper or reusable silicone liners.

2. Using an electric mixer, beat butter in a large bowl until creamy. Add brown and granulated sugars, then beat until fluffy, about 2 minutes. Beat in eggs, one at a time, until fully incorporated. Then, beat in vanilla.

3. In a separate bowl, mix together the flour, baking soda, and salt. Set mixer on low speed, and beat flour mixture into the butter mixture. Stir in oats and chocolate chips.

4. Spoon out dough by large tablespoonfuls onto prepared cookie sheets and flatten with a fork, leaving at least 1 inch between each cookie.

5. Bake until cookie edges turn golden brown, about 8 to 10 minutes. Centers will still be quite soft, but they will firm up as the cookies cool. Cool completely on a wire rack. Store in an airtight container at room temperature.

Note:
You can replace the chocolate chips with raisins.