Soybeans (where they fit your rotation) are also excellent early-season pull — green soybean leaves are highly palatable through August and September. They lose draw once they yellow and dry, which is when brassicas and clover take over.
If your property has none of the above, a fall-planted oat plot germinates in 7-10 days and produces a quick green draw through October. State crop calendars time the planting; variety reviews pick the cultivar.