I've done it both ways. Generally on new seedings I put a local multi grass mix in the large seed box and red clover or alfalfa in the small seed box of my GP NT1006 drill. When I see the alfalfa or clover getting thin I will graze it or mow it down low in the spring then no till drill whatever it looks like it needs. Sometimes I will just NT drill both grass mix and legume into an existing stand in the spring. Depends what the old stand looks like. I never till it at all except I use the Aerway ahead of the drill if going from corn to pasture/hay.

I try to alternate the legume to avoid alfalfa on alfalfa allelopathy but often as mixed as these stands are it doesn't matter and I end up with both alfalfa AND red clover in the stand as shown in the pic above.