Make microwave popcorn in the oven
I'll come out and say "no, you can't make microwave popcorn in a conventional oven."
For popcorn to pop, the kernel must reach a temperature well above boiling (which builds up steam, causing the kernel to explode). It must do so very quickly, otherwise the moisture will just slowly evaporate out, simply drying the kernel rather than popping it.
Microwave popcorn works because the microwave is primarily heating the kernels directly (because they contain the most water), and quickly. Air poppers don't use the oil, but they do get very hot, and the forced air heats the kernels very fast. And stovetop methods use the heat built up in the oil to heat the kernels quickly. Even fire-popped corn (a fun prospect) relies on fast heat.
Unfortunately, ovens are anything but fast. In the time it would take to heat the kernels, they would just dry out, and possibly start to burn the bag.
If you want popcorn without a microwave, stovetop popcorn is quite easy, and very tasty. I like using a wok, because it's shape is well suited for popcorn (sloped sides keep the kernels in the hot spot, while allowing popped kernels space to expand).
I did try it:
At 500°F the bag caught fire.
Seems like a partial answer, could be written more clearly - at the kind of temperature you need to pop corn, the bag catches on fire, so it doesn't work.
I did this just now but it took too long. Short answer: not worth the time. This became a 2 step process. I put the microwave popcorn bag in the oven, baked on about 400 degrees, long enough for the oil to melt. Once the butter melted inside, the bag got a little puffy, while still in the oven. I removed the bag, opened the bag and dumped the contents into a stove top pan, slid out like magic. Popped as usual on top of the stove. It tasted great.
I tried the convection mode thinking it would seal on moisture. At 500 degrees F the kernels did start to pop. However, letting the bag stat that hot so long made the plastic melt and the paper seams unglue. Sort of worked, but the burnt plastic smell was awful and probably chock full o' dioxins.