Featured Image and RSS Feeds

I read a lot of blogs, and use Feedly (on Chrome, and on iPhone) to do so.
I’ve noticed that for every post that appears in Feedly’s list, next to it there is a thumbnail preview of the image in the article. This is true for everything except for mine, where there is a blank square instead. When I insert an image into the body of my post, it accompanies the Feedly preview of my post. BUT (I think you’ll figure out my dilemma) I’d rather not have every single post contain both a featured image AND an image in the body in order for it to appear “the same” as the others. Does that make sense?

Any ideas how to get that featured image to be used as the one picked up by RSS readers, so that I don’t need to find two images for every post I write?

I hope that makes sense…