To remove the backgrounds from the featured post titles and dates on the Oxygen theme showcase page, add this to your Appearance → Custom Design → CSS editor:

.featured-post .entry-title a,
.featured-post .entry-meta,
.featured-post:hover .entry-title a,
.featured-post:hover .entry-meta {
    background: transparent;
}

However, I wouldn't recommend doing that because it may make the text really hard to read depending on the images you've uploaded.

For the future, would you please make sure to include a link to the blog you're working with when you ask questions in the CSS forum? Thanks!

I am looking for a way to remove the box around the Featured posts title. Would love to have just text with no box around it.

Thank you for any help you can give :)