Another nomination, if you include infectious disease epidemiology as part of biology and hence computational simulations of epidemics as part of computational biology:
Measles periodicity and Community Size, M. S. Bartlett, J. Roy. Stat Soc. A, 120(1), 1957.
The computations were run on the Manchester computer. Possibly the most entertaining part of the paper is the discussion afterwards from one of the computing assistants:
Mr. J. C. GOWER: I should like to describe in a little more detail the programme for the Manchester computer which has produced the results that Professor Bartlett has been discussing ... Owing to the fact that the computer makes not infrequent mistakes and in view of the apparent impossibility of getting an overall check ... it is necessary to repeat the calculations ... The random numbers are produced in batches of 64. Each batch is tested for divergence from the expected number of unit digits. If the test fails a new batch is produced and tested. If three successive batches fail the machine stops and hoots continuously.
Only once in the sixteen months during which the programme has been running have three successive batches failed ...
But the winner (also in population biology) might be the one linked in the comments to a Biostars discussion, Gene frequencies in a cline determined by selection and diffusion R.A. Fisher Biometrics 1950. On p. 169 the author says
I owe this tabulation to Dr. M. V. Wilkes and Mr. D. J. Wheeler, operating the EDSAC electronic computer
(the tabulation is the solution of the differential equation $\frac{d^2 q}{dx^2} = 4 x (1-q)q$ with boundary conditions $q=1/2$ at $x=0$ and $q=0$ as $x \to \infty$); the Wikipedia page about EDSAC (linked above) claims
[Fisher's study] represents the first use of a computer for a problem in the field of biology