I might as well jump on the bandwagon along with Matt Yglesias and Josh Marshall. Meacham, who writes nicely, was apparently on Morning Joe and said something to the effect that Lincoln and FDR didn't use executive orders. Matt and Josh raise some of the obvious points, the Emancipation Proclamation and going off gold.
I've been doing a little reading in the organizational history of USDA, and in the 30's FDR created and moved SCS and Resettlement Administration (forerunner of FmHA) around via EO's. I don't know why, but the pattern seemed to be that Roosevelt would act, then Congress would legislate.
(I suspect Meacham phrased his point poorly--that he meant that promising to lead by issuing EO's isn't very appealing. But FDR did promise "action" in his inaugural.)