Oatmeal Chocolate Chip Cookies

1 cup (250 mL) butter, softened
1 2/3 cup (400 mL) packed brown sugar
2 eggs
1 tbsp (15 mL) vanilla
2 1/2 cups (625 mL) large-flake rolled oats
1 2/3 cup (400 mL) all-purpose flour
3/4 tsp (4 mL) baking powder
3/4 tsp (4 mL) baking soda
1/2 tsp (2 mL) salt
2 1/2 cups (625 mL) chocolate chips

Makes 5 dozen medium cookies.

Line rimless baking sheets with parchment paper; set aside.
In large bowl, beat butter with sugar until fluffy; beat in egg and vanilla. In separate bowl, whisk together rolled oats, flour, baking powder, baking soda and salt - stir into butter mixture until combined. Stir in chocolate chips.
Drop by heaping 1 tbsp (15 mL), about 2 inches (5 cm) apart, onto prepared pans. Bake in top and bottom thirds of 375°F (190°C) oven, rotating and switching pans halfway through, until golden, about 12 minutes. Transfer to rack; let cool. (Make-ahead: Store in airtight container for up to 5 days, ha-ha if they last that long, or freeze for up to 2 weeks.)