We do not have research on corn gluten in vegetable beds. For weed control we recommend cultural practices such as mulching, handweeding, and cultivation.
Here is our we site on weed control http://extension.umd.edu/hgic/plants/caring-your-garden
and weed control in asparagus beds http://extension.umd.edu/hgic/asparagus
and onion http://extension.umd.edu/hgic/onions