Same room sex is not a foursome because physical interaction is limited to each couple.
If you are close to another married couple and are comfortable having these kinds of conversations with them, it's as simple as asking if they've ever thought about trying it.
We've done this twice. The first time was with a friend of mine from work. She and I talk about our sex lives once in a while, so I asked if they ever tried a threesome and she said no because her husband is the jealous type. But what about two couples having sex in the same room, but not touching each other? She asked her man. I asked mine. A couple weeks later, they came over for drinks and we had a lot of fun. She still mentions it to me sometimes.
It's worth trying, if you're that adventurous!
