I have been asked to make a 4-tier wedding cake for my niece with strawberry filling in each tier. The reception is being held outdoors in the middle of June. I usually use my favorite strawberry pie recipe for strawberry filling but have always refrigerated this. I'm worried about how well it will stay firm if not refrigerated, especially outdoors in the summer heat. I am having nightmares of red strawberry filling oozing out of the sides of my beautiful white wedding cake or even worse, layers sliding off!! Any suggestions for a good strawberry filling that will stay firm without being refrigerated? I have plenty of time between now and June to experiment so I'm open to any and all suggestions. Thanks!!!

Add strawberry jam to your buttercream. You need to heat it first so it's smooth. Let it come to room temp and mix it into your BC. This makes kind of a strawberry mouse-ish type texture and it's stable and taste yummy.

I use strawberry preserves, when I use it for filling i use more preserves than buttercream and when I use for Icing i just add a little for flavor. Make sure you use a thick buttercream dam so your filling don't come out if you won't refrigerate it will be very soft.
Good Luck!