Genesis - Change featured image size in the blog feed

1. In your WordPress dashboard, go to Genesis > Theme Settings > Content Archives.
2. Under Featured Image Size, select your desired image size.
3. Click Publish to save.

Please note that changing the image size in the Theme Settings will only affect the blog feed on your homepage and/or blog page. Images on category pages or in Genesis Featured Post widgets will not be affected (but can be changed separately).