Is it easier to get into graduate school straight out of college or after working for a few years?

 Depends. Some companies offer tuition assistance. So if it is a degree that will help them or your current job then maybe you can keep your job and get your degree for free.  This is the best of both worlds.  A masters in the same field you're in or an MBA would probably be covered if your company offers tuition assistance.  A few companies, example Texas Instruments, sends some of their engineers to law school.  If you work for a college or educational institution sometimes they will cover graduate work all the way to PHD studies.  In the past some independent school districts, for example Mesquite ISD,  have sent their teachers to Master and PHD programs.  There is also a program called the PHD Project that might be of assistance for graduate business studies.  You do not need a masters before pursuing a PHD.  I just put this out there if you are looking for an affordable way to get your graduate degree. Verizon has a tuition program that pays for undergraduate and graduate degrees, in addition to certifications. 

 You can also work and leave to get a graduate degree.  If it is an extremely prestigious program then it might be worth it but I could not say from personal experience.  I did leave my job to get a masters, but I had to take out loans and get a minimal part time job. Then I was able to get an internship in the summer.  I was hired after the masters at a time when the unemployment rate in information technology was less than 1 percent.  So the odds were in my favor.

I do not think that working after college hurts your chances of getting into graduate school. In fact, it will probably help. Graduate schools like to see the real-life experience and that you've developed professional skills. Especially if the job is related to what you want to study in graduate school.

Further, it will be easier when you start financially to have been working and earning some money.

Good luck!