One of my first bisexual experiences involved this scenario. Unfortunately, I haven't been able to find another couple to play with since...but what memories :)
I was close to this couple and the male and I had a few M2M experiences. One night he confided in me that he always wanted to receive oral while fucking his hot little wife. He wasn't sure how to make it happen since his wife didn't know that he was bi and he wasn't sure that he wanted another man to be with his wife. I suggested that we go to his house Saturday night after Happy Hour and suggested to him that we all get a good buzz on and see what happened.
Saturday came and we all got drunk at Happy Hour and continued to drink some good wine and smoked a joint or two. Previous to that night, I had it planned that if he would leave the room, then come back naked, I would take it from there. Dave left the room and came in stark naked with a hard on. His wife was taken back a bit and asked what was going on. I told her that I always fantasized about seeing those to fuck and just wanted to watch. Dave sat on the couch and it wasn't in no time that Brenda was bottomless and straddling Dave with her back facing his face. I got an excellent view of her shaved pussy and his hard cock. I suggest that he insert it into her and that she ride it. She started to do that and then I slowly went over and started to lick her clit while he was inside her. At first, she was startled, but she kept riding him and enjoying me licking her clit and trying to sneak a lick on his shaft. She had one or two orgasms and asked me to stop sucking on her clit for a few minutes as she rode him. I then worked my way down to his balls. I started to gently lick them and suck on his nut sack, because she was sensitive. I then begin to lick his balls and suck on his ball sack. I then worked my way to the base of the shaft and started to lick that. It wasn't long before Brenda came again, but Dave was only pre-cuming at that point. After Brenda came, I had her stay straddled on his lap but pulled out his 8 inch cock and began to suck on it. It wasn't long before he was shooting his hot wad in the back of my throat! I milked him dry as he grew semi- soft.
By this time, Brenda was hot again by watching her man shoot in my mouth. She wanted me to go down on her, and I looked to Dave for approval. Dave indicated that it was okay so I started to lick Brenda's clit and gently suck on the clit. The next thing I knew, Dave was behind me and gently rubbing his cock against my ass. I could hear him open up the lube and hear the lube being applied. Dave then inserted his cock inside my virgin ass (only a dildo was up there previously) slowly and then grabbed my hips and eventually started to fuck me hard. All of this while I am bringing his hot little wife to orgasm. Dave soon came in my ass and I was rock hard. He gave me permission to fuck his wife....so I did via doggie style. I was cumming in a matter of minutes! After that night, we pretended it never happened in front of his wife, but Dave and I still did the M2M thing and now added anal sex. It seems that he was fulfilling a fantasy of mine that night as well, that I forgot I mentioned to him! (and they say men don't pay attention....lol)