For a constant γ ∈ [0, 1] and a graph G, let ω γ (G) be the largest integer k for which there exists a k-vertex subgraph of G with at least γ k 2 edges. We show that if 0 < p < γ < 1 then ω γ (G n,p ) is concentrated on a set of two integers. More precisely, with α(γ, p) = γ log γ p +(1−γ) log 1−γ 1−p , we show that ω γ (G n,p ) is one of the two integers closest to 2 α(γ,p) log n − log log n + log eα(γ,p) 2 + 1 2 , with high probability. While this situation parallels that of cliques in random graphs, a new technique is required to handle the more complicated ways in which these "quasi-cliques" may overlap.