Can microwave safe glass vessels be used in an electric oven?

Sometimes. Basically, this is the same as asking if glass is oven safe:

Generally, glass is oven-safe if taken from room temperature and put in a moderate-temperature, preheated oven. The key thing is to avoid temperature shocks (which will cause the glass to shatter). Some glass is specifically designed for oven use (either by being tempered or made of borosilicate glass). Often glassware will say if it is safe for oven use or not, and under what conditions—check the packaging or instructions it came with.

You also need to take precautions when removing glass from the oven. Do not set it on something that'll conduct heat away rapidly, such as a wet countertop.

Before heating glassware, inspect it for damage. Scratches, chips, etc. make failure much more likely. This applies to the microwave as well.

Note that non-glass parts of microwave-safe glassware may not be oven safe. For example, if it has a plastic lid, that should generally not be used in the oven (even though its OK in the microwave).

edit:

In response to your update, that oven is what would often be called a toaster or countertop oven. Those change temperature much more rapidly than a larger oven (which can be electric as well). So, generally, you'd avoid glass in them.

But, your glass says it can be used over a flame, from the freezer. So it's clearly one of the very shock-resistant ones, possibly borosilicate. I wouldn't expect it to be a problem. Just make sure to preheat the oven.

Also, since you know who made it, you can of course contact the manufacturer to confirm.

Yes, they can be used

No, it's not a good idea. It's just too easy to make one small mistake which will result in at least a ruined dish, and at worst case glass shattering into your face

It's not worth the risk. What gain is there in using glass in an oven?

Even glass in the microwave can get so hot that it will crack/explode if put onto a surface with uneven heat (e.g. a single water drop on your work surface)

You can obviously use Borosil containers which is very safe indeed. I make most of the dishes in Oven and Micro oven with Borosil containers.

Thanks- Joshita