In large-eddy simulation of turbulent combustion, subgrid scale (SGS) scalar mixing must be modeled. Our recent study of SGS mixing in nonreacting jets shows two limiting SGS mixing regimes in which the SGS scalar distribution and structure are qualitatively different. These regimes could have a strong influence on turbulence-chemistry interaction in turbulent nonpremixed flames. Here we investigate SGS mixing in turbulent flames. The filtered mass density function (FMDF) of mixture fraction and other filtered variables are studied using measurements in turbulent partially premixed methane/air (Sandia) flames. One-dimensional filtering in the radial direction is employed to compute the FMDF and related variables. Conditional FMDF conditional on the Favre filtered scalar (mixture fraction) and SGS scalar variance shows similar trends to the nonreacting results. For SGS scalar variance small compared to its mean, the FMDF is not far from Gaussian and the conditionally filtered scalar dissipation depends weakly on the SGS scalar, indicating well-mixed SGS scalar. For large SGS variance, however, the FMDF becomes bimodal and the conditionally filtered scalar dissipation is bell-shaped, indicating the existence of a diffusion (dissipation) layer structure, which is similar to the mixture fraction profile in the counter-flow model for laminar flamelets. For the measurement locations considered (up to 30 jet diameters downstream) the mixture fraction jump across the layer is generally larger than the reaction zone width in the mixture fraction space, therefore the mixing field can support flamelets. The conditionally filtered temperature near the stoichiometric mixture fraction decreases progressively with increasing SGS scalar variance. Furthermore, local extinction events appear to occur mostly when the SGS scalar variance is large, suggesting the possibility of flamelet extinction. The results suggest that the mixing regimes and the mixture fraction structure could potentially have a strong influence on the combustion regime and extinction/reignition in turbulent nonpremixed flames.