Preheat & Prepare: Preheat the oven to 350°F (175°C) and line a baking sheet with parchment paper.
Mix Wet Ingredients: In a large bowl, whisk together the vegetable oil, eggs, and vanilla extract. Add the brown sugar and granulated sugar, stirring until well combined.
Combine Dry Ingredients: In a separate bowl, mix the flour, baking soda, cinnamon, salt, and oats.
Form the Dough: Gradually mix the dry ingredients into the wet ingredients until fully combined. Let the dough rest for 5 minutes.
Shape & Bake: Scoop 1 tablespoon of dough, roll into a ball, and flatten slightly on the cookie sheet. Bake for 9-10 minutes or until golden brown. Let the cookies cool completely.
Melt Chocolate: While the cookies cool, place the chocolate chips in a microwave-safe bowl. Melt in 30-second intervals, stirring in between, until smooth.
Assemble the Spiders: Fill a piping bag (or ziplock bag with the tip cut off) with the melted chocolate. Pipe a small amount in the center of each cookie and place a mini ice cream sandwich on top.
Create the Legs: Use the piping bag to draw 8 spider legs around the cookie.
Add the Eyes: Place candy eyes or small chocolate chips in the center of the ice cream sandwich.
Enjoy! Serve immediately or freeze for later.