1. Preheat oven to 350°F.
2. In a small bowl, use an electric mixer to cream peanut butter and brown sugar until fluffy. Beat in the egg.
3. Add rolled oats and baking soda to creamed mixture, and mix well.
4. Line 2 baking sheets with a Silpat mat or parchment paper.
5. Roll dough into 2-inch balls, and press to flatten on the cookie sheet.
6. Bake for 8 minutes or until the cookies turn slightly brown.
7. Cool cookies on a rack, and store leftovers in an airtight container.

Source: Calorie Count [2]