The WQXR follow-ons have me listening to composers I know (Fibich, Zelenka) and some new to me.
Today it was Hubert Parry. Now, I'm sure I've heard some of his choral music and occasional pieces, but his piece in the WQXR follow-on list is the Symphonic Variations of 1897. It is a fine, fine piece, beautiful and beautifully structured. So I went to Google Play Music, where I heard his Symphony No. 3, English, and will be hearing No. 4. Excellent music; beautiful, vigorous, rather Brahmsian (and I mean that as a compliment).
You might also want to check out Dame Ethel Smyth. I listened to some of her music last year, and it is wild, beautiful and often abandoned. I've never heard her opera The Wreckers but if it's as good as her orchestral works, it was a good choice. I hope to hear it live some day!
Update: Also, US orchestras looking for something novel that audiences will like: check out these composers too.