Abstract. We study the Fourier expansion of a function in orthogonal polynomial series with respect to the weight functionsIt is proved that such an expansion is uniformly (C, δ) summable on the simplex for any continuous function if and only if δ > |α| 1 + (d − 1)/2. Moreover, it is shown that (C, |α| 1 + (d + 1)/2) means define a positive linear polynomial identity, and the index is sharp in the sense that (C, δ) means are not positive for 0 < δ < |α| 1 + (d + 1)/2.