I love the intense bitter flavor of radicchio, but understand that it can be a bit MUCH for some. Me too. When I want to mellow the flavor of this lovely stuff, I take it to the grill. With just a few minutes on high heat, the radicchio gets that delicious salty sweet grill flavor that nicely balances its natural bitterness. Here's how:
1) Quarter your radicchio
2) Brush on all exposed sides with an olive oil, salt, and pepper mix
3) Grill, turning every three minutes or so until nicely caramelized - 6 to 9 minutes total depending on your grill
If you want to get fancier with this technique, try this.