Preheat oven to 350 degrees F (175 degrees C). Grease 2 muffin tins or line with paper liners.
Combine pumpkin, eggs, olive oil, and maple syrup together in a large bowl; mix thoroughly.
Combine flour, oats, baking powder, baking soda, cinnamon, and nutmeg in a small bowl. Stir into egg mixture. Add spinach and stir until evenly dispersed in the batter.
Spoon batter into the prepared muffin tins, filling the cups 2/3 full.
Bake in the preheated oven until a toothpick inserted into the center comes out clean, about 20 minutes. Cool for 10 minutes before removing from the tins. Let cool to room temperature, about 20 minutes.