Blood Types. A, B, & O are alleles. A & B are dominant over O. Each
person has only 2 alleles. What type offspring can an AO x BO parental
cross have?

Meanie, Punnett squares are terribly easy to construct. Go to it!

http://www.borg.com/~lubehawk/psquare.htm

Punnett squares are fairly straightforward to construct, and you could
probably even find that specific example of blood types if you had a
genetic textbook lying around.

But, in any case, here's how it works out:
AO x BO:
   |  A  |  O  |
----------------
 B |  AB |  BO |
----------------
 O |  AO |  OO |
----------------
(I hope that formatted properly!)

So the final result is, we could have AB, or AO, or BO, or OO
genotypes, corresponding to AB, A, B, and O phenotypes, respectively.
Each is equally likely, occuring once in the four possible outcomes.