Mine love just about anything, but won't eat anything bitter, like radiccio, escarol, mustard greens, etc. If I have a left over cantalope or watermelon, after cutting out the good stuff, I put those in there. They pick away all day and when they are done, all that is left is a piece of green "parchment paper". They love pasta, especially with a little marinara sauce, if any is left from dinner.
Mine have a bowl in their pen where I put the stuff (bottom of a 5 gal.bucket) and they will walk straight out in the morning, looking in the treat bowl. They sure love their treats and eat better than most people I know!