Proper advise would depend on where you are located.

If your area gets enough summer rain it is not too late for a short maturity soybean.

If you don't want weeds, you could spray the field 3 times with roundup/glyphosate now until fall planting.

Oats is a great fall draw, but usually dies over winter in the north. Winter Wheat is great too, and greens up the spring for double use. My personal favorite is fall planted white clover with winter wheat. I had great results with a $7, 50 lb bag of "feeder" winter wheat, came up great and the clover is looking awsome.