Dan DeLong has a suggestion for the NASA Centennial Prize:

1. first edible tomato over .1 kg grown at 5 kPa total atmospheric pressure
2. first edible potato over .1 kg ” ” ” “
3. first kg of edible corn kernels ” ” ” “
4. first kg of edible peas ” ” ” ” “
5. first kg of edible beans
etc.

Where 5 kPa is Martian atmospheric pressure and also a reasonable-to-build lunar greenhouse. If you make the winner of each ineligible for the others there will be a large number of contestants.

Each contestant gets to choose atmospheric constituents from oxygen, nitrogen, and CO2 in any combination.

Then, another series of prizes would be for food crops grown with 2 weeks daylight and not more than X% duty cycle and Y illumination intensity for 2 weeks, repeat cycle as necessary. Then, X and Y decrease to lower and lower values for higher dollar prizes.

I hesitate to extend the idea to animals because I wouldn’t want the issue to get confused by animal rights activists.

Unfortunately, things that are literally edible (they won’t kill you, and might even prove nutritious) don’t necessarily taste all that great. As I pointed out to Dan in email, there are a lot of items in the produce department of my local grocery (including tomatoes) that I consider inedible, at least relative to the home-grown variety. Maybe you could come up with a panel of judges to make a determination as to whether it was sufficiently edible to be useful to space colonists.