Hi, 

It depends on how much you applied, and this is assuming you have a tall fescue lawn (you wouldn't have overseeded a warm-season grass in the fall). Maryland has a law limiting the amount of fertilizer you can apply on lawns in a given year to protect the Bay, and a window for application restricted to March 15  through November 15. You can refer to the chart we have on our Maintaining an Established Lawn page for the rates. The product you use should state on the label the amount of time between applications if you need or can apply more this season. Usually, it is somewhere between 4-8 weeks, so if you haven't exceeded the rate of fertilizer for this season, then you could apply soon, before Nov. 15. We haven't had much rain recently, so be sure to water in the fertilizer as well (you should be watering for the overseeding too). 

Let us know if you have further questions. 

Emily