If you have a bare bachelor degree in Math, and you would like to pursue a master in EE, I would say this is rather difficult and probably unfeasible.
In the EE bachelor, so many topics of which most are applied (including labs) are covered.
Admission wise, with a bare math (i.e. not covering any EE courses) degree it would be difficult to get admitted since one would expect that there is a substantial numbers of engineers whom are applying where they will be given priority.
If you want to make up for the different in courses between Math and EE, basically you would have to make up for most technical courses except probably Engineering Mathematics and computer programming. You can see for yourself by checking any EE bachelor degree curricula.
If what you meant, was going for a bachelor of EE after a bachelor in Math, it should be smooth since you would be comfortable with all the mathematics that are typically new to other undergrad students.