To check the applicability of the Scully curve, a Random Effects Model was applied to MENA countries (1985-2015) using the Hausman test. Five out of the seven studied economic variables had a significant effect on the economic growth rate: Government Spending, its squared value, total domestic investment, the change in imports/ exports; whereas population and inflation rates had an insignificant effect. For Egypt (1985-2015) we relied on time series and a co-integration method was applied using the ARDL model. Results showed a significant inverted U-curve relationship between government spending and GDP. Their inverted U-shaped curve indicated that optimum Government Spending amounted to 25.95% and 36% of GDP for MENA countries and Egypt respectively.