Preheat the oven to 300 degrees F (150 degrees C).

Stir oats, almonds, pecans, and sunflower seeds together in a large bowl. Mix oil, honey, cinnamon, and vanilla together in a smaller bowl; pour over dry ingredients and mix well. Spread mixture onto two ungreased baking sheets.

Bake in the preheated oven until golden, about 20 minutes, stirring halfway through. Remove from the oven and let cool completely before storing.