Looks like a great spot for a food plot! I would start spraying whatever grass and weeds are there immediately. The sooner you can stop seed production the better off you'll be. If it's tall I would mow it down first, give it a week and then spray. Once it's all dead begin discing, tilling or whatever you plan to do to break up the soil. You will need to do this cycle as many times as possible prior to planting. The more you can do it the better your chances of having a weed free seed bed for your plot.
I'm not very familiar with oats and winter wheat so I'll leave that for someone else. Providing the soil is where it needs to be the clover and brassicas should do well. My deer don't eat chicory and only nibble at the turnips, rape and kale occasionally. I've talked to others that said their deer went nuts over that stuff. If the deer herd doesn't annihilate the clover it really needs to be mowed several times a year to keep it healthy and help it compete with weeds. A few times in the spring and again in the fall during prime growing time goes a long way to keep it thick and lush. Just something to keep in mind when you are deciding what else to plant with it. Part of it will be trial and error to see what your herd likes. Sometimes figuring that out is the hardest part.
Just curious, what kind of equipment do you have?