In this talk, we derive asymptotic expansions of the random coding union bound to the error probability, as the codeword length goes to infinity, in quasi-static channels. We approximate the pairwise error probability using the saddlepoint method, write the union bound as a tail probability, and then find a Taylor series in inverse powers of the codeword length. After the leading term in the expansion, namely the outage probability, the next two terms are found to be proportional to (log n)/n and 1/n, respectively, where n is the codeword length. Explicit characterizations of the respective coefficients are given for the quasi-static binary erasure channel, the quasi-static binary symmetric channel, and the quasi-static fading channel.