Yes, you can till and then plant right away as long as you didn't till in anything that needs to age like fresh manure.
Nothing wrong with planting right in the ground, especially if you have plenty of decent soil. The reasons people do raised beds are generally either that they have very limited space and want to garden it very intensively, or they have very bad soil (very heavy clay or very sandy, too acid, too alkaline, etc). In the bad soil example, it is a lot easier to get to good soil just by filling a bed with it, than by amending the ground.
If your soil is decent, go for it. But understand that since you didn't start with a whole bed of hand built enriched soil, you will have to work a little harder at enriching your ground. If you have compost, fall leaves, or other organic amendments or whatever you will be fertilizing with, spread it before you till and till it in.
Here's an OK planting guide:
https://osufacts.okstate.edu/docushare/d ... 004web.pdf