1. Preheat oven to 325°. Line 2 baking sheets with parchment paper.
2. Beat butter and sugars at medium speed with an electric mixer until creamy. Add eggs and vanilla, beating well.
3. Combine flour, baking soda, and salt in a bowl, stirring well. Stir in oats. Stir oat mixture into butter mixture, blending well. Stir in chocolate.
4. Drop batter by 1/4-cup measurements onto baking sheets. (Space cookies about 4 inches apart.) Flatten slightly.
5. Bake 15 minutes or until edges are browned and centers are set. Let cool on baking sheets 3 minutes or until firm. Transfer to wire racks to cool completely.