Adjust oven rack to middle position and heat oven to 375 degrees F.

In bowl of electric mixer or by hand, beat butter until creamy. Add sugars; beat until fluffy, about 3 minutes. Beat in eggs and vanilla; beat until well combined.

In a separate small bowl combine flour, baking soda, salt and cinnamon. Gradually mix into butter mixture with wooden spoon or large rubber spatula until just combined. Stir in oats and butterscotch chips.

Drop the dough by heaped tablespoons onto ungreased baking sheets (or, parchment-lined baking sheet*), leaving at least a 2-inch gap between each mound. Place one baking sheets at a time onto center rack of preheated 375 degree F oven. For soft chewy cookies; bake until very lightly browned, about 7 to 8 minutes. For crisper cookies; bake until golden brown, about 9 to 10 minutes. Cool on baking sheet for at least two minutes before transferring to wire rack to cool completely.

Makes about 48 cookies.

To make Bar Cookies: Grease a 10- by 15-inch jelly-roll pan. Spread cookie dough in prepared pan. Bake until light golden brown, about 18 to 22 minutes. Cool completely in pan on wire rack before cutting into bars.

Store cookies in an airtight container at room temperature for up to 1 week. Cookies freeze well.

*Note: Parchment paper is not a necessity but does make for easy cookie removal and cleanup. If using parchment, remove baking sheets from oven and immediately slide cookies on parchment directly onto cooling racks.