Can put something in the oven if its already microwave safe?
No, just because it's microwave safe does not mean it's oven safe. The thermal mechanisms involved in microwave radiation and convective heat are completely different. Many plastics are microwave safe, but you should never put plastic in the oven.
Technically you could put them in the oven, but if you are planning to turn the oven on, I wouldn't recommend it. If the dishes are plastic, as most dishes labeled 'dishwasher and microwave safe' are, then they will melt if used in the oven. A microwave is safe as its only a few minutes, and a dishwasher uses hot water.
You can put plastic in a microwave oven; many microwave-safe containers are made of plastic, and most plastic cling-wraps are suitable for microwave use. Some plastic bags are fine for using in the microwave oven. If in doubt about any type of plastic, read the data on the packaging or check with the manufacturer or retailer.