Hi @mikejanssen,
What version (Elementor, Gutenberg or Shortcode) of The Post Grid plugin do you use? It’s very easy to change the font-size with Elementor and Gutenberg version. But there is no option to change it in the Shortcode version. So If you use the shortcode version you can simply put the below css in [Appearance > Customize > Additional CSS]
.rt-tpg-container .rt-holder .rt-detail .read-more a {
font-size: 20px !important;
}
And if you use Gutenberg or Elementor you can change the font size from – Style tab -> Read More -> Typography.
Thank you