Prep the basics: Heat the oven to 350°F (175°C). Line two baking sheets with parchment.
Set butter, coconut oil, and egg out to warm slightly if cold.
Cream fats and sweeteners: In a large bowl, beat butter and coconut oil until smooth. Add honey and brown sugar, then beat until light and creamy, about 2 minutes.
Add egg and vanilla: Mix in the egg and vanilla until fully combined. Scrape the bowl so everything is even.
Whisk dry ingredients: In a separate bowl, whisk flour, baking soda, baking powder, salt, and cinnamon.
Combine: Add dry ingredients to the wet mixture.
Stir just until you no longer see streaks of flour.
Fold in oats and mix-ins: Stir in the rolled oats and your chosen add-ins until evenly distributed. The dough will be sticky.
Chill briefly: Refrigerate the dough for 20–30 minutes. This helps prevent spreading and gives thicker, chewier cookies.
Portion: Scoop 1 1/2 tablespoons of dough per cookie (a medium cookie scoop works well). Space 2 inches apart on the sheets.
Bake: Bake 9–12 minutes, until edges are set and lightly golden but centers still look soft.
Cool: Let cookies rest on the baking sheet for 5 minutes, then transfer to a rack to cool completely.
They will firm up as they cool.