Preheat the oven to 350°F (175°C). Line two baking sheets with parchment paper.
In a medium bowl, whisk together the rolled oats, all-purpose flour, baking soda, salt, and ground cinnamon. Set aside.
In a large bowl, using an electric mixer, cream the softened unsalted butter, granulated sugar, and light brown sugar together until light and fluffy, about 3 minutes.
Add the egg to the butter and sugar mixture and beat until well combined.
Mix in the plain Greek yogurt and vanilla extract until fully incorporated.
Gradually add the dry oat and flour mixture to the wet ingredients, mixing on low speed until just combined. Do not overmix.
Using a tablespoon or cookie scoop, drop rounded spoonfuls of dough onto the prepared baking sheets, spacing them about 2 inches apart.
Bake in the preheated oven for 10 to 12 minutes, or until the edges are lightly golden but the centers remain soft.
Remove the cookies from the oven and allow them to cool on the baking sheets for 5 minutes before transferring them to a wire rack to cool completely.