Shader over several text gui nodes

Hi! I have a gui that contains 4 dialog options stacked on top of each other. Each dialog option is a separate gui object. Like so:

I want to run a shader over all of the dialog options. For example:

What’s the right way to set this up? A shader on the containing box doesn’t seem to affect the text. Do I need to add a backbuffer to the render script, or can it be done by just enabling a material before rending text?

Thank you so much!