Preheat oven to 350°F and prepare a baking sheet with parchment paper or a silicone baking liner.
In a large bowl, add the softened butter* and granulated sugar. With a hand mixer, beat on high for 30-60 seconds or until fluffy and light in colour.
Add the brown sugar and beat again. Add the egg and vanilla extract and mix well.
Add flour, oats, baking soda, salt and beat or stir with a spoon until all ingredients are well combined.
Using a cookie scoop or a spoon, scoop out 1-2 tbsp of dough, roll into a ball and place on the baking sheet. Repeat with the rest of the dough.
Using a fork, gently flatten each cookie to ~1/2" thickness*. Bake for 15-17 minutes or until golden brown on the bottom of the cookie. Let the cookies cool for 5 minutes before enjoying!