Preheat the oven to 375°F (190°C). Line two large baking sheets with parchment paper. Whisk the flour, baking soda and salt in a medium bowl, then stir in the oats.
Cream the margarine, brown sugar and granulated sugar in a large bowl with an electric mixer at high speed until well blended. Add the egg and vanilla, and beat until light yellow and creamy, about 3 minutes.
Blend in the sour cream with a wooden spoon. Add the flour mixture all at once and blend until just combined (don’t overmix or the cookies may become tough). Stir in the chocolate chips.
Drop dough by heaping teaspoonfuls about 2 in. (5 cm) apart onto the baking sheets. Bake until golden brown, about 10 minutes. Cool on the baking sheets for 2 minutes, then transfer to a wire rack and cool completely. Store the cookies in an airtight container for up to 2 weeks or freeze for up to 3 months.
Nutritional Info: Each serving (1 cookie) provides calories 85, calories from fat 22.5, fat 2.5 g, saturated fat 1 g, cholesterol 7 mg, carbohydrate 14 g, fibre 0 g, sugars 9 g, protein 1 g