Indeed they can. The custom cattle that we raised very much enjoyed apples. Even though they started as range cattle (which for the uninitiated, are very capable AND willing to kill you if you get between a cow and her bawling calf) after months of being made to eat their vegetables before dessert (apples), they would come when called and eat the apples from one's hand.
They liked their corn. That tote has about 1500lbs of rolled corn, and that was just one of many.
Well I'm just a podunk ex farm-kid, but where I'm from corn was considered a type of grass. At least, before Roundup-ready corn was invented, Roundup would happily kill it while largely not affecting broadleaves. That's what we had 2,4-D and Banvel for. 30 years ago, I'm talking.
And to further add to this discussion, not only will cattle eat various and sundry plants, but your tame 4-H steer will also happily eat a McDonald's Quarter Pounder right out of your hand if you let him.