Preheat oven to 350 degrees F.
Grease 9x13" baking dish, and set aside.
In large bowl, combine oats, cinnamon, baking powder, and salt. Stir to combine.
In a separate bowl, whisk together honey, vanilla, coconut oil, milk, and eggs.
Add to oat mixture, stirring with a spatula until combined.
Fold in rhubarb, strawberries, and walnuts.
Pour into prepared baking dish.
Bake in preheated oven to 40-45 minutes.