Preheat oven to 350°F. Spray a 9 x 13 baking dish with cooking spray; set aside.
In a large bowl, combine oats, chia seeds, chopped peanuts; mix to combine.
Melt peanut butter and honey in the microwave or on the stove top. Add to other ingredients and mix until moistened. (You may need to use your hands to get the dough really well mixed. If it still seems too dry, add more peanut or honey 1 tablespoon at a time until moistened.) If desired, you can fold any add-ins into the dough at this time.
Press dough into greased dish and bake for 10-15 minutes.