question about priority
 

Today i played a game of Munchkin with my friends and this happened:
player 1 and player 2 fought the monster together. Player 3 threw in a wandering monster making them loose the combat. Player 1 tried to get rid of one of the monsters with polymorph potion and i played Out to lunch. Here's the question: Does he still get to draw the treasure?

Re: question about priority
 

This is a good question - Pollymorph removes one monster from combat, and then Out to Lunch ends combat entirely.

But, since there is no "stack" in Munchkin, you'd need to resolve each independently. Pollymorph would remove Monster #1 from combat, and enable treasure for that monster. Resolved. Out to Lunch then only acts on the remaining monster, ending the combat against it without allowing treasure.

TL;DR - I'd allow the first monster's treasure to be drawn.

Re: question about priority
 

I'd say that out to lunch ends combat and there is no treasure to give out. You have to defeat the last monster to earn any treasure. No defeat, no treasure.

Re: question about priority
 

Out To Lunch overrides any other cards and gives you two Treasures, period.

Re: question about priority
 

The rules are specific about this: No rewards until all Monsters are defeated. So, Out To Lunch overrides it, and as Andrew said: Two Treasures. Period.